The reason for the 3 weeks gap is so that you can get as close to 100% doing the feedback.
Living in Manchester it would have been a 200 mile return journey North or South if I had to resit any exam.
For me, failing an exam by one mark by answering one question wrong that I already had in the feedback would have been too much for me to take
Also another tip I can recommend is, just before you go into the exam have a single page of relevent facts that you really struggle to remember and write them down from your refreshed memory the first thing after the exam starts. i.e. stuff like DME frequencies or PFD colours arrrggghhh
FIS.