Hi
I have the same issue and it appears that it is the starter motor is at fault . a known issue for series one cars . The replacement starter is in fact a modified LHD BMW /Bosch starter .Apparently a big job - at least 8 hours to fit !!
Mine doesnt work one in ten attempts . Much worse when hot ....If left it will get worse until it packs up so best to get it sorted if this is the issue
Mine is on order and my really helpful dealer is sorting me out -
