surely you can get a cheap budget flight to exeter if you book now??? it's like 20 minutes from the airport!!!
www.flybe.com
honestly, anyone wanting to come to this from far away, it's WELL worth looking at that site...
i think there's hotel's in seaton too, but check with the promoters for the best ones... if it was me, i'd get a flight down, bus to seaton, check in, have a WICKED nights, get some sleep, get the bus to exeter, check in and you're home!!!!
mark