Went out yesterday at 7am and it was only 3c, so wore longs, short sleeved top with arm warmers and lightweight gilet. Started off a little chilly as the first mile is downhill, then it's 3 miles of climbing so was nicely warmed up by then and the rest of the ride was perfect.
Im not sure I buy into the cold knees thing though, I'm a postie and wear shorts for work unless it's sub zero - with last years mild winter I haven't worn trousers for two years. Unless it's really freezing my legs just don't feel cold.