First of all, does your employment contract stipulate that you will work in a particular store? It would be unusual if it did in that manager's are usually expected to be flexible.
Are you still on the same conditions, salary etc as when you went off on sick leave?
You should talk to your HR department or MD if the intention is to keep you at a store that is unsuitable to your disability. Legally, they should make reasonable adjustments to accommodate you. If that's not possible then you may find yourself being offered a job at a different store which may be suitable to your disability. If no such store exists and they cannot reasonably make changes then you would probably be made redundant, but this would be unusual if it is a large company with a number of stores to choose from. Usually, teh bigger the company the less excuse they have not to make changes.
You should also discuss with your HR department or MD your future role within the company. They need to tread carefully if you are genuinely disabled.