My friends just got back from London and while they didn't love their hotel they were very happy that they had their own thermostat that actually worked (since they like a room at near-sauna temperatures).
But given the availability and price of gas in Europe this winter, you might not be so lucky esp. if you're staying at an apartment rental or a smaller hotel. So if controlling your own temp is important to you, contact the location in advance and confirm what their plans are. Heat could be a real budget-buster for many lodgings this winter. I learned the hard way back in the '80s that Brits don't heat the house, they heat themselves with layers of clothing.