Need some info to answer this - when did you plant it? Where did you buy it from and was it outside when you purchased it, or under shelter, or indoors?

Maybe the poor thing got 'shocked' by the move - is that what you're suggesting, Bamboo? That's what it sounds like, doesn't it. A warm environment to cold - too much for the poor plant.

Yep, that's what I was wondering, Spritz - it may have needed hardening off first but also, and somewhat surprisingly after all the wet, it's been bone dry here in London for over a week and believe it or not, the top couple of inches of soil were cracked and dry, so drought might, just might, be a possibility, though not quite as likely.

Yes - I've had the watering cans out!