Be hosest, as someone else mentioned its freshers week so they will be in the "first time properly away from home stage, can do what I want etc etc"
90% probably wouldnt want to get a meaningful relationship out of anything that happens
(well maybe you can lie about where you live and say you live closer to exeter)
another option since you are unlikely to see them again, think of the most outrageous/almost unblieveable story you can, and try to put it across with a straight face
if it works you have a "interesting" life and if it doesnt you were just joking around and have a good sense of humour.