Southern conductors both before and after the major DOO / OBS implementation could (and can) be rostered for up to 10 and a half hours on weekdays, longer on Saturdays and longer still on Sundays. Considering there's basically no way they can leave a train if it becomes delayed, that has been known to effectively result in regular 12 hour days on certain bits of the roster, once you also take into account getting to work in good time.
In other words, the OBS role's hours were broadly accepted in one form or another for conductors, and as such have actually never been a highlight of the RMT's opposition to the various parts of the rollout of DOO trains and the OBS role.
I don't believe there's any industry/occupation in Great Britain where trade union membership is permitted to be compulsory, though the railway industry is probably as close as it gets to making you feel that it is.
If by the "Micky mouse" Union you mean TSSA, it definitely is recognised in some places, but membership is often so small as to have little clout if said union calls out its member (not a typo) on strike at a particular location! Not that they'd necessarily want to do that anyway.
