Hi Rob,
Have a look at:
http://www.ukgser.com/forums/showpost.php?p=3253463&postcount=12
To be frank, the synthetics / synthetics and wool mixes (Helly Hansen, for example) are good, too.
Anything sold for skiing, rock climbing, running, yachting will probably do you.
I prefer the ones with a 6" zip at the neck, whilst others prefer a turtle or polo-type neck. But that's just a personal choice.
I use mine summer and winter, T-shirt or long sleeved, according to temperature, layering (or not) on top.
Leggins, much the same story. I have Helly Hansen's of two different TOG (or whatever they call it) ratings. Great in winter or in very hot weather, particularly under leathers but just as good under a textile suit, too.
Things to look out for, if possible:
(1) External seams, are good as they save rubbing.
(2) Fit. This seems obvious but it is important in the neck area, which bods often forget. You don't want it too tight or, worse, so bulky that you cannot get other layers on top, then your Buff and still do the jacket collar up.
(3) How well the fabric stretches is something to have a gander at. Many have some sort of 'stretch' polymer built into the weave, which is a plus.
(4) How quickly they wash and dry. Most are now very good. The wool and synthetics being a big improvement on plain old cotton or crude sheep's wool.
Have a look at several in a shop like Cotswold or Millets or whatever and see if you can try on before buying. It saves a lot of time and effort in the long run, trust me. If you can stretch to it, the Merino wool ones are great.
PS For real all-day cold*, little beats an electric waistcoat or underjacket. Pricey though and watch that it doesn't draw more than 5 Amps on first turning on, or you'll trip your CanBus out..... or fit a relay... or go straight to the battery via a suitable fuse.
* or even that March pre-dawn hour dash down the motorway to the Chunnel.
