Today I popped over to my friendly local tyre place and in exchange for £20, they swapped over my summer tyres/wheels to the winter set. The summers (which were filthy) have been thoroughly cleaned, first with Bilberry and then with Dragon's Breath and are currently drying outside. They'll be put in the shed later on.
Normally, I'd pop some sealant on in a few weeks, but as the car is going in March, I won't be bothering this time. The summer set will be going back on the car on collection day (provisionally 1/3/17).
I also discovered a nasty scratch (long, not deep) on the front wing, so I will try out my new(ish) Rupes dual action polisher and see if I can sort it out.