Erm...an (un)educated guess and by checking the R and Mk5 forums!
The R ones as they have overspent on their cars, the Mk5 ones as they sorely need upgrading!
The cost of your retro-fitted GTI is creeping towards R territory with what you have planned for it. 
Creeping very,very slowly, but not and never be there.
Still at least £3500 less than a base R when everything done.
My mistake, thats not so bad then. 
Phil: I have worked out the exact price difference between the Golf R and a GTi.
The price difference for a basic 4 door is £6430.
With factory fit Bi-Xenons on the GTi, this difference will be £5330. With retro-fit Bi-Xenons, this difference is £5000 approximately.
As I also had to install rear LED lights as a retro-fit, this difference 'for me' is now £4580. This is still a considerable difference.
The GTi, whichever way you look at it, is still very good value for money in comparison.
