In reply to richnew.:
For me the key is to be able to add layers on top as it gets colder/wetter, which usually happens on the way up, and to take layers off from the top when it gets warmer/drier, usually on the way down. What you don't want to have to do is to take several layer off in the cold/wet to allow you to add another mid warm layer.
A couple of things - Scotland is wet (100% humid) but not necessarily really cold, and when you move you'll get hot and sweat, and when you stop you'll get cold. Wicking and breathing materials may work well in cold dry climates like the Alps and Norway, but in Scotland expect to get damp and dress accordingly using material which will keep their warmth when wet.
Therefore as an example my system for typical Scotland winter climbing is as follows -
One or two merino long sleeved base layers
A micro fleece
A softshell (I personally don't like the Rab vapour rise material and prefer a single skin material like TNF which is tighter fitting) - This is what I would normally walk-in wearing, unless it's raining, because I don't want to over heat.
At some point when it starts getting colder, often at the gearing up point at the start of the climb, I'll add another warm layer over my softshell. I've got a Rab waist coat thing with synthetic insulation. I'll then put my hardshell on top of this.
If it gets colder still I'll add my belay jacket, also synthetic insulation, on top again.
Post edited at 09:38