Hi NF43
A couple of mates of mine went to a school in Exeter called Flightpass and did their FI(A) Ratings. They said they had great training, it was very professional and really enjoyed their time.
If you you're looking down South you may as well consider the Southwest as well. Check them out.
As far as prep, swot up on the PPL syllabus and brush up your technical knowledge. The rest is done on course.
Good luck with your training where ever you go
Regards
D 'n' H