UKH

Is the lack of a gore Tex membrane an issue for wet Scottish winter climbing?

No, not in my experience.

Same here. My Nepal Extremes are over 20 years old now, I don't use them every winter but when I have done in recent years they still seem as waterproof as when I used them loads in the first decade of their life.

Don't know about Extremes but Nepal Evos soak up loads of water even with a membrane.

Interesting. Have you waxed them? On my original Nepals I just covered all the visible yellow leather in a load of old school nikwax. I've always been impressed with the results. 

I didn't, I had a pair of yeti style gaiters kicking about so I just put them on.

Edit: as an aside, I've put yeti type gaiters on a few pairs of boots and they've worked really well but some people seem to be dead against them for some reason.

Yep, I've still somewhere got my non Berghaus but yeti style full foot gaiters, Terra Nova I think they are. I've also found they work very well. I've used them on the Nepal Extremes ice climbing in Arctic Norway in March when it was pretty chilly and I survived with all my toes intact. But even by then, about 15 years ago, the trend setting guides and sponsored heroes had all seemed to have packed in wearing gaiters as they made you look like a punter or something.

+1, you do need to re-wax leather boots from time to time, otherwis I can imagine at least 4  possible consequences:

1. boots soak up water and get heavier
2. wet boots can freeze
3. if no waterproof lining, I guess the leather could eventually saturate and soak through but I think they'd have to be pretty wet for ages(?)
4. leather can dry out and eventually crack if not waxed.

No, my Nepal extremes are 14 years old. They are very heavy compared to modern boots, but honestly they are awesome, so well built.  Never had wet feet

I had an old pair of non Goretex B3 Boreals. UK winters would wet them out and they would freeze. I suffered with cold feet and was glad to see the back of them. Can't speak for the Nepals.

Now you have jogged my memory I also covered mine in Nitwax. 

Still use my 15+ year old ones, treat the leather occasionally and they are fine. They have to be one of the best ever made boots after the original Scarpa El Caps and Dunlop suretread wellies. (Both now extinct).

Mine are c.20 years old, I think on their third pair of soles. I wax them like any normal leather boot. It ruins the photogenic yellow look but keeps my feet dry enough and the uppers are still in good nick. 

I'm almost certainly in a minority but I'd rather not have goretex in a boot. I don't have particularly sweaty feet but goretex loses its breathability once the uppers are caked in mud and effectively turns the boots into plastic bags. I do see the point of membranes in some fabric boots but not in leather boots. 

So in general I'm getting the feeling they are bit of outdated but still perfectly workable with the right care and consideration. Nikwax and proofing seem to be essential