I think the autumn months are the best time for city breaks. There is something nice about being able to wear a blazer with a thick coil of wool scarf and be sufficiently warm. With a few layers and even a jaunty hat, you're cosy and comfortable.
Plenty of art galleries, a Brick Lane curry and a few pints make for a very good weekend.
PS. This was my first proper time in London, would you believe? And is it a cliche to say, that I...heart it very much indeed..