The Rapha Festive 500

riding in low temps (i.e. just above freezing) - would I be better to run my wheels with wider tyres (32 front, 38 rear Vs 30s on the otherwheelset) or is it a much of a muchness ?

Riding in the cold tyres (and tubes) get stiffer/slower. I believe already stiff/slow tyres will be affected more than supple/fast tyres (but there are other valid reasons to run stiff tyres in winter).

‘Good’ tyre size and pressure relate to ride+bike weight and surfaces. I don’t see how temperature would influence these but maybe I’m missing something.

TL:DR just run whatever you’ve dialed in as comfortable, fast and safe. As you would any other temperature.

{ caveat : I’ll be riding the 500 on 40mm knobbly tyres so don’t listen to me }