E46's didn't come with LSD's (other than the M3), if you want one it will be an aftermarket unit. There's a company called Birds which fit one for around a grand I think.
Thanks for the reply. I know that the E46 didn't have an LSD as standard - I was looking for a second hand one as I don't really want to spend 800-1000 on a car that I'm not going to have for more than and 1 & 1/2 years....