GFT
 

Is it possible for your own instructor to do your GFT?

NO!

Quite apart from the fact that there is no such thing as a GFT

Someone will no doubt be able to quote Stds Doc 19 on this but paraphrasing . . .

You cannot take the PPL Skill Test with anyone who has taken any part in your training. However, the examiner is allowed to have carried out 'safety check flights' on you during training.

If we're talking CPL Skill Test then the examiner cannot even be a member of the same Flying Training Organisation (unless you're on an integrated course).

Yes - another triumph of eurocracy at PPL level!! Presumably this ruling was introduced because the rest of JARland is so corrupt that they can't be trusted to do things impartially? My syllabus now has specific 'Progress Checks' which 'should' be flown with a UK/FE; these flights are 'safety checks' to confirm that the student, sorry, 'applicant', has reached a satisfactory standard for that part of the course and, quite deliberately, contain no new teaching points. Because some of my volunteer FIs are also FEs, if they conduct these 'Progress Checks' then they 'may' conduct the 'applicant's' PPL Skill Test if necessary. But if they have flown any other exercises with the 'applicant', then they 'shall not conduct the PPL Skill Test' for that 'applicant'.
Sorry about all the inverted commas, that's because they indicate JARspeak terms!