Jonnie,
I'm in central Scotland, so I'm riding in similar weather to you (dull, damp, dreary and dreicht, but at least the winter's better)
I use either Castrol 4T or Halford's 10W-40 Motorcycle oil (Bugundy container)
I'm not using any oil between changes.
Some people have reported that when switching from mineral, or semi-synthetic oil to fully synthetic that they do get higher oil consumption, and that by switching back again the oil consumption drops.
So it all depends on what your engine's been used to.