Lots of aerospace industry in and around Bristol. Not sure if you're talking specifically flying work as the closest experience you could hope to get would be some operations type work at a flying school, say Aeros at Filton etc.
Engineering wise, you've got Rolls-Royce in Filton - I recently spent 6 months there, and it looks very good on the CV. Not sure if they take summer only placements though. Your Uni should have a person to contact about such things. Also you have Airbus and Cameron Balloons. There's also probably a lot of smaller aerospace companies supporting the big ones.
Good luck!