Thanks for all the replies!

sirbuynsellalot can you explain a bit more?

I did notice its the same engine as the st, so there could be some parts out there, and i thought 38mpg would be achievable as i regularly get 36... although it could make far less difference than i hope!

I know just buying an st would make more sense (or even just the 2.5v6) but my thoughts were that it could be possible to get v6 performance without the terrible economy. although i'm thinking now maybe it would just be better to save for the 2.2tdci...

if anyone does know how much things would cost though I would be very interested, and any views on remaps?