I think Asker is having another one of those "moments" 
I have a Tig R Line DSG and it's a great alround car, nothing like some of the opinions I have read here. Also it's based on a Golf (not a renualt) and shares a lot of the suspension with the Passat. I much prefer using the Tig in London than the GTI.
However I would say buy the Mk6 GTI 5 door instead (but that's only because I want to sell mine
)
You and I both know that Steve...
Common platform to the Mk5/Mk6 Golf/Passat...same Haldex 4x4 system. ETKA tells you what's common...dash = Golf Plus, suspension a mix and match, as you say.
Tig R-Line is a nice car...not cheap if you hit the extras (£37k I get to), but a good car that drives like a Mk5/Mk6 golf.