Thanks for the replies, guys. I think I'm going down the disc lock route. I'll get one of those luminous springy things that you tie to the grip to remind you to undo the lock.
EXACTLY! The solution is to use the luminous leash, that you then reach up to a lever, or somewhere along the side of the bike.
It also adds as an immediate visual deterrent, so the thieves eyeing up the bike, will see that leash from a distance.
Fitting onto the rear wheel is better if possible, as the rear wheel is much more difficult to get off (if they go to extreme measures to bypass the lock)!