Welcome to my country! But it is a very very different place, inasmuch as I can judge - I never knew the UK countries from inside though I always enjoyed visiting.
A) Grimbergen EBGB is the only small airfield near Brussels. Grass only, VFR only, very strict procedures. Even there, "self-fly hire" is not a common concept, either you own your own craft or you hire from a club. We do have genuine - i.e. "not for profit" aeroclubs, here, actually most small aerodromes are operated by one.
B) No, shares are rather exceptional, though not totally unheard of.
[[edited to add]] and if setting up a syndicate, be warned about the scarcity of hangar space. My own homefield EBZH has a livid waiting list, last time I inquired there were only 10 to go
EBCF Cerfontaine seems to have permanent vacancies but it might take a Ferrari or Aston-Martin, driven with a lot of urge, to cover the distance in one hour, especialy on a Friday afternoon after work.
C-D-E) no answer, I know little of EASA licensing as I am on a sub-ICAO license. But I seem to understand one can basically fly an EASA plane on an EASA license in all EASA-land.
Generally: I know quite a few UK expats in Brussels, they are massively giving up UK nationality in favour of Continental citizenship, Belgian mostly. Especially since Brexit, now just guess why?
And - slightly ironic, but still - if you are "by no means fixed on a life in Belgium", you may have some things to learn yet. How to pay taxes, for a beginning...
180 € per hour sounds more like Holland, though, you should be able to find better in Belgium. Do be prepared to join a club, though, and that would involve some degree of club activity, too - like assisting in the annual cutting of trees near the runway, or turning the spit or cleaning the loo at the (equally annual) club festivities.