Hi DoggBoy!
Firstly I need to say...GET A CROSSFIRE!
They are a very rare sight here in the UK and look very classy. I have had my fair share of cars including an MR2 - 53plate convertible facelift model. At the time I liked it however comparing an MR2 and XF - The cars are in a different class.
XF is a Merc in desguise and is a real head turner - The MR2 is reliable but cramped and boring to drive.
I travelled 185 Miles from Southampton to get mine and it was worth the train journey up!!
Always remmember...If you see one advertised that looks to good to be true - It is! So just walk away.
I managed to get mine for £3800 is black 04 with 72k on the clock FSH 9 months MOT taxed, cracking car. Im glad you have done your homework!
You will notice a large amount of XF's in that grey/Silver colour as they are very common and generally cheaper - Id go for black or dark red if I was you as they generally have more kerd appeal and easier re-sale!