Winter training, geared or SS?

I stick to fixed, just makes cleaning and maintenance much easier.

I thought going fixed in winter was the way to train...maybe just the old boys in my old club?

Going SS will save you trashing your derailleurs and make maintenance a doddle, but if you're actually training (rather than just riding for utility or pleasure), then FXD is the way to go.

You will develop a smoother pedalling action, or "souplesse" as the French say, and learn to pedal at a higher cadence.

BITD they just used to strip the derailleurs off their Summer bikes and swap-out the wheels.