Standards Doc 11
Standards Document 11: JAR-FCL Provision and Conduct of Ground Examinations for the Private Pilot Licence Aeroplanes & Helicopters (including Registration of the Training Facility & Authorisation of Examiners) | Publications | About the CAA
says (for both pass and fail):
The GR should indicate areas where weakness has been found, but should not discuss answers to specific qurestions.
Which is new, I think, and certainly better.
IIRC, previously if you passed with only one question wrong, i.e. theroretically you knew all you needed to except for one single weakness, they weren't allowed to tell you what it was!
Another practical exam tip is that (from memory) the easier questions are at the end, you may want to do them first because it is easy to run out of time doing nav.