Try "The Fast Club" at
http://www.fastclub.co.uk/ they have a Cherokee Six. No other SEP like that based at Exeter.
Exeter Flying Club's largest are two Cessna 172s
http://www.flying-club.com/ , Flight Pass
http://www.flightpass.co.uk/ have Cherokees.
Perhaps the Broussard G-YYYY at Eggesford (25ish miles N of Exeter) might be an interesting idea?
http://www.devonstrut.co.uk/ click on the airfields link then that for Eggesford.
The Dunkeswell parachute school has a Cessna 206. I don't think it has any passenger seats though, or a door!
