I was wondering last year if i'd be better off without my mini as I never got to drive it much. Both me and my wife worked in the same place so drove in together in the Honda and I didn't really have any need to go anywhere by myself so we always took the Honda at weekends as my wife doesn't like the bumps in the mini.
Oddly though, as I was beginning to think what an effort it was to keep when i never used it, things changed. When our daughter was born, my wife took maternity leave, so we needed to have the Honda at home for her and bub. So I would commute in the mini.
Then in November I didn't get my contract renewed and got a job in the CBD so it was train commuting from then on. The mini pretty much sat there gathering cobwebs most of the time (even went to a morris minor & mini show n shine and won the Post 1990 category without touching the car, cobewebs, dust, coke cans on the floor and all!!)
Having a baby also meant that we would take the Honda most places.
Then in January we bought a $150 baby seat from Target on special and put it in the mini - it was the best thing i've bought for the mini all year - i've now taken my daughter (she's 1 year old on Friday) on 2 long mini runs and she loves it and gets lots of attention too!) I think she prefers it to the big car as she's closer to the driver and has a better view out the front and sides too.
Then as my wife's gone back to work, the daycare we ended up in is a couple of kms away and so I now have to do the drop-off and my wife does the pick up, so i need the car every day again.
You never know what's around the corner, so if it's not about money, just park it up, take care of it and consider re-registering sometime in the future.
As for the 500 register, i'd probably give it up, see if someone else wants to take it over in the UK. If no-one steps up, then maybe wind down your involvement and let others take the strain, even if they don't take the whole thing on lock stock.....
(I'm in the same boat with the mini club here, haven't got around to joining, never seem to get around to speaking to the right people when i'm at an event, and i am the worst person at sending cheques and forms through the post (don't even have a chequebook anymore) Still have every intention of joining, it'ss either happen just by chance or if they have an online option at some stage

)