Nick,
A good +4 is an excellent starting point!
But corrosion of any form shouldn't be an issue on anything after they introduced stainless steel bulkheads, rot proofed the ash coachwork replaced steel wings with thermoformed alloy and galvanised the chassis. these changes didn't arrive together but were in place by about 1998 - 1999.
Since then there have been detail improvements, but a 2010 car should be close to perfect, fully undersealed and as the exhaust is now stainless there isn't anything to corrode. Yes there may be a bit of surface rust on the suspension bits, brake drums, especially if it hasn't been used much.
Go to Morgan dealers and have a look at the cars they offer. Don't buy privately unless you are confident you knw as much as about a Morgan as the seller!
Good luck!
