Mines a 2.5, thankfully i havent had to find out yet. I was told fobs can be got off ebay, but dealership prices are into the 100s, so i decided i didnt need a spare fob! Assuming you have the fob, a key wouldnt need the immobiliser code?! perhaps? maybe?
They do stock a lot of keys there. I am a bit freaked out by my local. Had some keys cut, and they were duds so he offered to come round and make them fit. Very creepy the way he said I. I suggested he should cut them properly from the pattern instead in order to uphold the good name of his company!
I may be wrong but I think that the immobiliser coding is within the key for both the Mark 2 and 2.5. I think the remote fob is just for the alarm as I believe you can still open the door with the key, which sets off the alarm, and then start the car which somehow resets the alarm.
No idea on the price of a key though. Timpsons is probably a good bet or those key cutting franchises in some of the supermarkets maybe.