http://www.threadnaught.net/~caleb/ukserpen.html

you would if one bit you on the ass! Unlikely though. Light brown, with dark brown diamonds on its back I think. Only proper snake in britain anyay. Like to bask on rocks in the sun. Like most 'dangerous' animals, are usually more frightened of us that we are of them though, so unlikely to go for you.

As Ocifant said, loads of us here love Cornwall, and I'm sure you will too.