Hi Paczo,
You seem to have organised your ideas very well and there is no reason that you shouldn't go forwards to enjoy learning to fly.
As to which school to use it's best to make your own mind up by visiting all those on your list and seeing which one welcomes you best and which makes you feel 'right' about using them. All the airfields you list have good schools available but one thing to bear in mind is that Coventry is constantly under threat and at present is scheduled to close in the coming summer.
Never, ever, pay up front for blocks of training as schools go out of business with frequent regularity!
I stand to be corrected but I think the language test can be done as part of the RT exam so most schools should offer that. As for reading material there is no harm in starting with what you've got (principles of flight and meteorology don't change for political reasons!). You can update what you need along the way.
If you intend to do the full Part FCL-PPL (A) then you will need a Class 2 medical which you can do with your nearest AME shown on the CAA website. If you are intending to only do the NPPL then a Pilots Medical Declaration will suffice. Only renew your Class 1 if you intend to go professional.
Good Luck.