Hashman
Thomson and Thomas cook - Thomson Airways Engineering
Ryanair - Ryanair Engineering
Easyjet - SR Technics
Air France - Engineers from Bristol Flying Centre
KLM - No based maintanance but have used Flying centre in the past.
BMI - BMI Engineering (I believe)
Thomson, Ryanair, SR Technics and I believe BMI all have office facilities in the Admin Building (Old Terminal), and Flying centre engineers are based at the flying centre.