How about riding the highest road in Britain......what Bealach Na Bar in Scotland you say, a bit far for a club ride. No that's the highest road open to cars. The highest road, I've read, is up to a Radar station in Cumbria: Great Dun Fell 847m, not open to cars but open to cyclists and apparently tarmac all the way. It would be a 160 mile ride though.
... sounds suitably bonkers....
The calendar looks a bit chocker for this year now, but you may be able to squash it in. Alternatively, keep it up your sleeve for next year?