Cheers for all the replies ... I spoke to the guy at BMW and he's text me a picture of the log book and it's classed as an 'M3 Dakar S-A' which he classes as a Sequential Automatic. He also HPI'd the vehicle and it came back Automatic.
I know there's arguments for and against, but I thought it best to stick with this, despite the increase in cost.
Anyway, I've insured it now - a little more than I was hoping to pay, but I wanted to pay monthly. Just looking forward to driving it off the forecourt tomorrow morning, probably using the manual transmission
...
Thanks again for the help.