Why does nobody ever want to tell us where they're travelling FROM?
BA operate to Geneva from Heathrow (with seasonal flights from Gatwick)
easyJet fly to Geneva from Bristol, Edinburgh, Gatwick, Luton. Liverpool, Southend and Manchester (with seasonal flights from Belfast International, Bournemouth, Glasgow, Leeds/Bradford, Stansted and Newcastle)
FlyBe operate seasonally from Cardiff, Exeter, Inverness, Isle of Man, Jersey and Southampton.
Jet2 fly from Leeds/Bradford,and seasonally from Belfast International, Glasgow, Manchester and East Midlands.
Swiss International fly from Heathrow and London City.
Thomas Cook fly seasonally from Manchester.
Thomson fly from Manchester and seasonally from Birmingham, Bristol, Edinburgh, Glasgow, Gatwiock and Luton.
Travel information, from the airport to CERN, is here:
http://outreach.web.cern.ch/outreach/expos_cern/plane.html