There probably wont be a GTI diesel. There will however be a 170ps 2.0 TDI Golf very soon. It is rumoured to be the GTD or just a GT TDI 170. It will be with us before the summer.
Discount on GT TDI 140s will vary wildly from dealer to dealer but 500 quid is a good deal. People will get more. Now is the time to buy as we work on a quarterly basis and dealers will be chasing targets. They will want the car registered before 31st March so expect good deals on stock cars. From tomorrow I will authorise my guys to go to 8% for march registration on Golfs (except GTI and R32 obviously). Expect an additional 500 quid off Golf Plus as VW is chucking money at dealers to shift them this quarter.
Hope this helps
VWmaindealer