The biggest factor is how much space you need. There will be a rising tariff usually linked to how many square feet you want. You can rent in sizes, such as up to 25 sq feet, 50 sq feet, 100 sq feet, 150 sq feet or 200 sq feet. The longer you’re planning to use it, the cheaper it becomes. And in terms of cost per square feet, the bigger the storage area rented, the cheaper it becomes… …Even with national chains, there are local variations. And if you don’t need regular access to your possessions, travelling further can lower the charges. For instance, the Big Yellow Self Storage Company in Brighton charges £172 per month for 100 sq feet, in Oxford it’s £192, while in Wandsworth, south-west London, it’s £233…

Check for additional expenses, such as up-front deposits, charges for accessing your storage room, paying for your own padlock or for using lifting and carrying equipment.
“Consumer Test: Self Storage” by Sean Deacy on The Guardian

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