Cheers for the welcome guys!
Smeagol - insurance is ~1600 with Just Car,although i'd avoid them if you reckon a claim is likely. Am considering Shannons as i hear they're much better with modified cars,although they only cater to "enthusiasts" meaning you'll have to be a part of a local car club.
I had a Z4M prior to this one and insurance was lower. Think it's got something to do with lots of 17 and 18 year olds getting 3'ers as birthday presents