mabs - I know what you mean. I am a big sweater and have been in shorts and short tee (Marmite or Teacake with a Protective Japanese Sun that is too wee if others in wash) for several weeks. It starts off a little chilly but as RTC says you warm up. I detected a little perspiration on days with less wind and just the other day the wee flies have all appeared.
However, the guy who sits next to me is still in long sleeved specialized top quite heavy weight fabric) and long tights. You see, he feels the cold. Partly perhaps because I have seen more meat on a butcher's pencil but also I think just because he feels the cold.
What we all agree on is that it has been absolutely cracking weather since we started the 'Had a lovely ride today' string weeks back. And many of us have been taking massive detours on way to work or way home because it has been such brilliant weather for cycling in, whether we are wearing too many clothes or not. [maybe they all take their jackets off just round the corner from where we spot them as they are too warm now?]