
Depends if you want to carry it as an extra jacket to sling on at stops or for emergencies etc.
If thats the case then I'd suggest looking at a Primaloft insulated jacket - TNF redpoint or similar.
I've got an ME one that I picked up cheap a couple of years ago, and its great.
I also use a Rab Neutrino Endurance down jacket for when its REALLY cold.
If its for all day use - then you're not going to want something that warm, you'll simply get soaked by sweat. If so then go with the Paramo suggestions as one of the often quoted compaints is that they can be too warm for mild weather.
HTH
Si