VW UK are a pain to deal with from my experiences and are very annoying. But at the end of the day you've modified the car during the warranty period, raced the sh!te out of her round the track on a regular basis and now she's a bit broke if I'm understanding correctly. It's not surprising they're not playing the game?....
I feel your pain but I wouldn't take this one on a no win no fee basis if I was a lawyer 
I have spent a lot of cash on the GTi maintaining/modding it, and whatever it needs it gets due to the way i use it, if something mechanical breaks etc, i know ive modded it and use it properly, i havn't tried getting these things done under warrenty i pay the indy specialist to get it fixed,
As for a gearbox leak from the mechatronics unit why should this happen, my gearbox has never been off or touched, this all boils down to me not taking my car to them for servicing, i have spent a fortune in this dealership over the last few years on vehicles but that means didly squat to them,
I wont be setting foot in the place ever again, they make my piss boil
will i buy another VW after this one ? maybe! not from there !,
anyway moving on its booked in for Monday at the indy to sort the leak out.
