It sounds like it's going to be a bit frosty when I get back. That'll be a bit of a shock to the system after a week of mild california weather!
Currently, according to my desktop widgets, it's 6°C here, but only 1°C in London. It'll be something like 17 hours before I get back to London, so you'll have had a days worth of warmth, and it'll be cooling down again.
Actually,looking at the forecasts, it looks like the weather is just going to be getting progressively warmer when I get back. The chances of a white Christmas (at least in the bottom part of the UK which I've checked) looks pretty remote.