It's likely that VAG don't offer an official map because they try hard to balance power with economy and remaining compliant with the latest Euro emissions as well as having an official CO2 output figure for taxation reasons. Aftermarket options will always be available, but if VAG officially alter the output, that creates all kinds of taxation implications as well as possibly not meeting Euro 6 compliance. Apart from that, who'd buy an R if you could remap a GTI officially for significantly less than the difference? Same with buying a TTRS over a TTS etc.
2/3 of your £2k is probably going on that drive train warranty.