As has been said before, at least GATCO membership fees can be claimed back from HMRC; wonder why Prospect membership can't.
Several years ago, Prospect suddenly raised membership fees for those on salaries over (I think) about £35K and I worked it out as an increase of some 15% when inflation was about 3%. I'm not sure there's any point remaining a retired member of Prospect, although retired membership of GATCO still brings some benefits.