Picture posting is enabled for all :)
When you say "London", its a big place! There will be differences in temperature all over.I live just north of London on Essex/Herts border in an exposed spot in the Lea Valley. The wind sweeps down, the frosts roll down and the water collects - so in winter it can be pretty cold. In summer, there is less rain than the surrounding area, and the sun bakes the heavy clay to something resembling concrete. Some years, frosts have been as late as second week in June.Relatives and friends who live in London Boroughs such as Enfield, Waltham Forest and Redbridge seem the be able to put tender plants out at least 4 weeks earlier than me. Particularly where they are in a built up area - one is able to leave pelargoniums out all year round, albeit in a sheltered spot, mine die and rot away.
Rob, if you know what area you're likely to move to, why not get on to the Metcheck website and type in a postcode from that area, then you can see what's happening and compare. It won't be perfect of course, and very general, but it might help. And when you arrive, let us Londoners know - there might be one of us just round the corner...Rob? ROB? Why are you cancelling the removal van? ;D