You will be able to count hours logged previously towards the minimum requirement, but you should expect to take a few (or more than a few) hours more than the 45 in total, partly because almost everyone does, and partly because you will naturally have to revise much of what you learned before, as flying skills diminish if not used.
For advice on schools near London, search or scroll down a few pages, as the subject has been covered in threads from earlier this year.