Seems a shame to do this to a UK TT6.
-----
TBH mate, I think you've asked too many questions to realistically get answered in a single thread. It'll be all over the place and hard to follow by the time everyone has chipped in with their opinion.
-----
How much of this gear will you be fitting yourself? If none, who will be fitting it for you?
-----
Fuelling:
I wouldn't go mad upgrading the fuelling. Stock lines, stock FPR, FPD, stock rail, single uprated fuel pump (Bosch or Walbro are the usual favourites) and some good quality 650cc/800cc drop in injectors - that should about do it. All IMO of course.
-----
ECU and mapping.
Choose a good mapper carefully. He'll be the best one to advise on which ECU would be best for you. As your car is a manual you have a wide choice of decent ECUs.
-----