I often have a peep at the webcams at Booker and White Waltham (not a million miles from Denham)
Skycams - Sky-facing webcams from around the UK, for weather forecasting and flight planning is quite useful for this (use Chrome or FF though, takes ages in IE)
I've had some lovely flights in the winter - still, sunny, and sodding cold. At least you engined lot have heaters - I've had to supplement my ski gear with extra layers before!