County Court confusion!

Rent Arrears

I would appreciate some advice and clarity of the following: I recently attended Oldham County Court in order to try and recover some outstanding rent from a tenant who signed an AST in December 2009 for a fixed term of one year that was due to start on July 1st 2010. The judge informed me that as the AST was signed prior to the tenant taking possession of the property, the lease could be void. He cited the provisions of section 52(1) Law of Property Act 1925 and the case of Long vs Tower Hamlets. I have never head of this before. All my tenants are students and sign in December/January for the coming academic year. The judge also stated that I should decide what sum I wanted to settle for as his decision would be a full and final settlement of the whole amount due for the year. I have only claimed for rents that have become overdue as I assumed that I could not claim for rent that had not yet become due. I did intend to issue a second claim as further rents became overdue.
I have previously been informed that once an AST has been signed by both parties, this contract is then legally binding on both sides and that the tenant has an obligation to pay even if they did not take up residency. Another replacement tenant has not yet been found.