Hi

In a YB running 340bhp, a 10w-50 is likely to be the best choice

http://www.opieoils.co.uk/c-659-10w-50.aspx

The Nanodrive CFS is, on paper, the best oil available, but the Pro S and CFS are both really good oils, so all are good choices for your car.

Cossiemainful is right about the stability and cold viscosity of something like a 5w-40, but it might be a little thin, especially if it gets hard use.

Cheers

Tim