As MrAgerage says...
Training providers, whether ATO or DTO have to stipulate to the CAA which syllabus they will be following. In the case of most DTOs, like us, they will be picking one of the propriety brands.
In our case, the syllabus, the written material (textbooks) and any on-screen briefing notes all follow the same format, even down to the same graphics so there is a consistent thread running throughout.
As said above, wait until you settle on a particular training establishment and see what they recommend.
Also, as above, steer clear of books that don't reflect the current syllabus, it's harder to unlearn stuff that is plain different from what you'll need to get qualified in the UK.
Re the on-line exams, we were told at the seminar I attended that the current text books and exam prep books were appropriate and no re-writes will be required. This seems to be borne out by the recent announcement that there is a good pass ratio with the new exams.
You won't need the medical to get started with the flying, unless you want to see if you will actually be able to continue at all, which I can understand.
TOO