Thanks a mill for the replies guys.

Lucifer, I'm such a dope, forgot to say that it's an E36. Luckily short of the CANbus there's no multiplexing going on as far as I know.
For researching and getting info on US cars versus UK/Ireland models, unfortunately I've been bitten by that once or twice before so I'll be doubly sure to check my sources.
Thanks for the reminder though, far too easy for me to follow a guide on bimmerforums and take it as gospel.
As for autostart I'm avoiding it like the plague and will hopefully be able to reassign it's button on the remote to something of use. Far too many horror stories and I really don't fancy installing something that bypasses my key chip for the sake of a slightly warmer car in the mornings once or twice a year.

I'll send you a PM now.

JohnC
Thanks a million for passing on the number. If I get stuck tomorrow (horray for long weekends!) I'll give him a ring.
With good guidance, properly soldered and heat shrunk joints and a bit of patience I should be able to manage it. If not I'll at least know my limits