In reply to fire_munki:
Central Cairngorms are your best bet early season, for mixed climbing. In the good old days (1980s) we used to start there in November, move around with the conditions, and finish up in the high Ben Nevis gulleys in May.
However, there always seemed to be a bit of a hole around Xmas with driving rain and blanket thaw, I hardly ever remember doing anything interesting in the week between Santa and New Year, and not just because of hangovers!