No idea, but if it were me I'd start by looking at where in Switzerland you can actually fly to from Bristol as that will likely be the deciding factor. There may be closer airports, but it may not be possible to fly to Bristol from them, and getting >1 flight will likely tote up the bill.
Any search engine should get you there, or you could check EasyJet/Jet2/BMI (I don't even know who operates out of Bristol though).