I have just read the Auto/Moto tests (French magazine) and was a bit surprised at their results. The test protocol seemed very thorough but what surprised me was that all but snow covered roads you were better off with a summer tire.
Breaking on wet roads from 100km/h at 8C. The Continental Contisportcontact 5, a summer tire would stop you in 53.3 meters, the shortest distance of all the tires. A Bridgestone Blizzak would take 59.7. On dry roads at 7C the Conti took 36.2 meters and the Blizzak 45.1m. Other winter tires were up towards the Blizzak. Not an insignificant penalty at what are not unusual winter air temperatures except in cold alpine valleys.
On the snow the Conti takes 35.4m to stop you compared to Blizzak which takes around half the distance of 18.4m from 40km/h with an air temperature of -9C. Now that IS a serious difference and a real win for the Blizzak. All the other winter tires were within a meter of the Blizzak. I’d be interested to see figures for dry/wet roads at lower air temperatures to see how the Conti does.
The moral is, for the Steppes of Surrey or even downtown Geneva you are probably as well to stick to good summer tires year round.
As for your ski trip. All I can say is that I run winter tires from November to May and like others can’t remember when I last fitted chains although I do remember when I last stopped on a climb because of ice which I would have made it over had I fitted chains. I just didn’t want to take the risk for a few hundred meters extra.
The resale on ebay idea is interesting and if you can get a good deal, perhaps from a French/Swiss garage, would not cost you much money? Beware that garages get their stocks in at the start of winter and may not have any winter tires after New Year.