I live in Australia in a climate not probly too far removed from southern US and have travelled to London many of the past 10-15 years for work and pleasure, often in November. Now November can be reasonably nice but if the wind gets up its bone-chilling cold. January would be a whole new level of pain. It's only going to be practical to be out between 0930 and 1500 and many tourist sites will not be open at all (so look them up for starters) . Having said that I still remember going to see the Victory when I was a kid and I love London....just consider waiting til it thaws out in April and that Pip has lived there many years so is use to winters (and may dissolve his Metamucil in scotch on certain days of the week). Great city but, eh mate!