Life in a consumer society is life with stacks of stuff, from books to pianos, clothes and coffee tables. In periods of limbo - when people are moving house, redecorating or getting divorced, for example - much of this goes into self-storage.

The Self-Storage Association (SSA), says that 230,000 Britons have goods in storage. However, prices vary considerably between companies and areas, and they are often inflated by unexpected extras, such as one-off fees and insurance.

People choosing a storage company may be going through a divorce or enduring the stress of relocating - not the best of circumstances for poring over small print - but it pays to do your research because annual costs run into thousands. Here Times Money offers a guide to storing your property.

What is self-storage?

This is the rental of a storage room or container in a secure centre. The “self” bit is important. Customers must pack their own goods, get them to the centre, stack them and lock them in with their own padlock. However, most companies have trolleys and lifts to help customers to shift boxes. Some, such as Henfield Self-Storage, offer free collection or van hire with a minimum storage term.

Storage spaces, or units, can be accessed in working hours and sometimes - often at a premium - over extended hours or 24 hours a day.

How much space do I need?

This is critical because space determines cost. All storage companies can talk through your requirements over the phone or face to face, and most have “space calculators” or quick guides on their websites.

As a rough guide, the contents of the average studio flat fit 50sq ft of storage. However, a conversation is best because your needs may not be typical. Remember that online estimates assume tightly stacked boxes. If you need easy access to items, more space may be necessary to accommodate routes in.

How much does it cost?

Storage space is not cheap. Pricier centres charge more per square foot than West End property rental agents. For example, I was quoted a rate of £56 a week to rent 50sq ft at Safestore in Holloway, North London. That equals £1.12 per square foot - 34p more than the rental on a Mayfair flat with Foxtons.

Rates hinge on a number of factors. Larger spaces cost more but should be better value per square foot. Location is all-important. Access Self-Storage quoted £273 for two months' rental of a 75sq ft unit in Islington, North London, but £195 for a 125sq ft unit in Manchester.

Unless it is part of a promotion, you will also need to factor in van hire - from about £30 a day self-drive - plus boxes and bubble-wrap for packing. The latter are available from the storage companies and cost between £50 and £100 for the contents of a home.

Bear in mind that you may have to store goods for longer than expected. Frank Boot, of Shurgard Self-Storage, says that many customers store goods for ten months after intending to store them for two or three.

How can I compare deals?

This takes effort because potential customers typically have to telephone or complete an online form to obtain a quote. To minimise complications, ask several providers - in your area and farther afield, if practical - for a written quote that factors in all extras and promotions.

An initial conversation with a centre manager is best, but ask whether you would be better off applying online as internet discounts are sometimes available.

Rodney Walker, of the SSA, also advises visiting centres to get a feel for facilities and service. Whether or not you visit, you should establish where your unit would be and how it can be accessed - some companies charge more for ground-floor units.

Prices varied widely for a 50sq ft unit close to my North London home. I was quoted weekly rates - after brief initial promotions - of £56 with Safestore in Holloway, £41.25 with Big Yellow Self-Storage in East Finchley and £38.08 with Access Self-Storage in King's Cross. With no special deals, Henfield Self-Storage at Staples Corner quoted £20 a week.

Many companies, especially the smaller ones, are open to negotiation, and some, such as Safestore, offer “price-beating” guarantees.

The SSA has a locate-a-store function at www.ssa.org.uk. Members include the big-name companies, such as Access and Big Yellow, and must abide by a list of standards (also online). Smaller non-member companies can be found in the Yellow Pages, local phone books or through a Google search. The Store Room, in the North, is one non-member chain with competitive prices and impressive testimonials, including one from Lancashire County Council.

Hidden extras

Most storage companies state that their pricing structures do not feature hidden extras. Watch the small print, however. For example, Shurgard charges a one-off registration fee of £10 and also requires customers to buy its own “custom-made” lock for £9.99.

Also check whether prices include VAT, where applicable, and be careful not to compare rates per calendar month with those for four-week periods because the latter covers fewer days. And note that a refundable deposit may be payable in advance.

Insurance

The SSA requires members to verify that customers have insurance. Some companies insist that customers have to buy cover through them at rates of about £5 a month per £1,000 of goods, sometimes demanding a minimum level of cover.

This could be an unwelcome add-on if your possessions are already covered by a home contents policy, and it may require you to complete a lengthy inventory of your goods. Check the situation with your insurer and storage companies. Non-SSA members may leave it to you to decide whether you require cover.

Promotions

Most companies run offers, although details vary between centres. Deals tend to give several free or cut-price weeks if you sign up for a minimum period. Shurgard is offering one month's storage for £1 with no minimum stint, but consider the extras detailed above. Discounts may be available to those who pay upfront for long-term storage.

Penalties

If you fail to keep up rental payments, a self-storage provider may deny you access to your goods and sell them, deducting the sum owed from the proceeds. Check terms and conditions for details. Also check notice periods and penalties for leaving storage ahead of schedule.

Alternatives

Rather than put goods in self-storage, you may be able to call in a favour and use space in a friend or relative's basement or garage. Alternatively, there is a brisk trade in garage space on Gumtree.com, the listings website. Lock-up garages with storage of 150sq ft go for as little as £20 a month. Dealing with individuals is higher-risk, however, and best considered with low-value goods.

Case study: The store room's flexible service measures up

When Stuart Thacker downsized from a house to a two-bedroom apartment last year he needed storage in a hurry and decided to look at a local company. The 47-year-old sales consultant, of Preston, Lancashire, visited The Store Room in his home town to discuss requirements. “The centre was clean and the staff were helpful,” he says. “I had no idea how much space I would need, but their assessment was spot on.”

Mr Thacker initially paid £168 per four weeks rental of a 120sq ft unit. Two months later he was able to move many of his goods into the redecorated portion of his new home and shifted the remaining boxes to a 25sq ft unit - at £52 per four weeks - for a further six months. He paid a total of £745, with insurance.

“I think that is very good for the service I received,” he says. “I chose to buy insurance, but there were no hidden costs at all. I was moving on my own, so was very grateful for the extra help they gave me.”

The company collected Mr Thacker's boxes from his home “as a favour”. He adds: “That was a big help because van hire would have been a real hassle. And the staff helped me to get my boxes into the unit. Not that it would have been a problem otherwise - we used trolleys and a lift.”

It's cheaper to let go

A safestore spokeswoman told me that about a third of its customers keep goods stored “indefinitely”. However, the cost of long-term storage can be staggering. For example, if you were to hire a 50sq ft unit in North London, pay by direct debit and then forget about it, you would shell out more than £2,000 a year with the big companies.

Some goods that go into storage would be better sold or binned. You could try selling them at eBay.co.uk or a real-world auction house. Alternatively, list them on Freecycle.org, a website that allows members to offer free items for others to collect. A garage sale is another fun option and could be combined with a party for friends and neighbours if you are moving from an area.

The Furniture Re-use Network, at www.frn.org.uk, has details of charities that will collect furniture or appliances for redistribution to those in need. Some charity shops may also be willing to collect significant gifts - large numbers of books or records, for example - while a number of dedicated charities will collect old PCs to refurbish for use in the developing world.

Even if you do decide to put goods into storage, you may find that you do not miss them and are willing to sell them or give them away.