"The basic £850 FRE is deemed to cover all potentially allowable expenditure by the employees concerned (other than travelling expenses) except:
•The provision of uniforms, where these are required to be worn but are not provided by the employer (see EIM50053)"
Uniform, if not provided by the employer can be claimed seperately, as can noise cancelling headset.
BALPA? Gives a level of legal cover in case it really does go wrong. If you join an airline which has union recognition you may wish (or not) to support that negotiating body.