My car was BPU from Whifbitz who do kits off the shelf.
With an 18 year old side mount IC it still made 421! So you may be able to save a bundle initially.
As has been mentioned, all the bits and pieces are listed and all very straight forward with the possible exception of FCD and Boost Controller.
You could always get the kit, do what you can, and if not prepared to travel too far I am sure TDi North in Warrington could fit anything you didn't.
Might also want to see if there are any club members who could help with the more complex bits. I would offer but would be about as much use as an ashtray on a motorbike!