The CAA wanting to support the organisations who support it by paying it massive licensing fees.
Privatised ATC having to invoice "somebody" for everything.
Job demarcation within ATC.
Re your Class E comment, airspace sovereignity is the stumbling block to any major European airspace harmonisation. (Yes I know the US system works a lot better).
That's a start, anyway
However, one sometimes wonders whether the status quo is actually better, because sometimes changes are done without much thought for GA. Take PRNAV for example - a totally poorly thought through idea which would push the vast majority of GA out of IFR airspace should it be introduced in significant enroute airspace.