So far I have used them with just cycling shorts on a cold frosty morning at 3 degree C and they were fine for me. Below freezing I may wear some thin tights.

Slightly confusing question - I am assuming you are asking if these are suitable for cold weather use...? The trousers are a shell - a thin waterproof fabric that is worn over your other clothing, so yes, it is suitable for cold weather use (note that a lot of ski clothing (etc.) uses GoreTex fabrics) but you need other suitable clothing as well. I prefer this as it makes them more versatile - you can chose how warm to layer on the day. This means the trousers can be used throughout the year rather than just in the winter as they are too warm the rest of the time. I currently wear mine over my normal shorts, but as winter starts setting in I shall wear thermals underneath to keep me warm. The trousers have no thermal insulation themselves.

Yes (it's the GoreTex Performance Shell if you want to find out exactly how waterproof from the Gore web site).

1. They use the performance shell.
2. The leg length from crotch to end of trouser measures approx 84-85cm on my size large.
3. I'm about the same waist size and they fit fine - loose enough that they don't dig in when bent forwards in a cycling position with a fair bit of scope for tightening with the adjusters on the waist.