lets see:
Scotland
winter conditions - snow
driving rain
gale force winds
Cold

Folks this is not the time to be as conerned with weight as with survival.

Bill#1,
If you look at the winter camping section of these forums you will see that there are almost no posts there. Also look at the mountaineering section - again no posts - why? Because only a handful of us are climbers. You need mountaineering type gear - bombproof gear that won't fail you, NOT light weight gear. You may be looking in the wrong forums.

A two person tent is best for winter solo, and a 3 person for two people in the winter unless it has a massive vestibule for the gear. Summer solo tents let in spindrift through the screen, have inadequate poles for snow load, and in fact, they were not designed for ANY load at all on them, AND they are too small for all your winter gear. Not to mention what gale force winds would do to them - most people here have "forest caping gear" not mountain type above tree line gear.

In short - 40 pounds for weather like that is not too much. In fact you may need a tent costing over $500-$600 to be both lightweight and bombproof, like my Bibler ElDorado. I just pitched my TNF mountain24 on one of my decks in the rocks behind my house. My Bibler would have been up in 5 minutes, but at 4.5 pounds, the trade for its weight and strength is that it only has 2 poles and can flap in strong winds affecting my sleep. The Mountain 24 ( a double wall tent)took 35 minutes to set up in a driving wind and I know this tent and have set it up under similar conditions before. I HATE double wall tents. Well I love em when I'm inside, but like all backpacking trades, do you wanna like it because its light to carry, or because its warm and cozy in camp? In winter you have to go for warm and cosy in camp.
Jim