I think as tyre technology develops, there is no generic answer to this question; because the tyre design and materials need to be optimised for specific climate conditions.
Imo some winter tyres could be a hazard for general UK winter driving, when there are more days over 7c than under; so a tyre optimised for Northern Europe/Scandinavia where -40c can be encountered, may be pretty rubbish on an average UK winter day, and offer very low levels of grip at 10c+ on a wet winters day.
Even if you want to run 2 sets of tyres, I think the best all-season tyres are a better bet for UK winter use than generic full winter tyres; and the window to change your tyres over is much larger this way for optimised driving.
Imo some winter tyres could be a hazard for general UK winter driving, when there are more days over 7c than under; so a tyre optimised for Northern Europe/Scandinavia where -40c can be encountered, may be pretty rubbish on an average UK winter day, and offer very low levels of grip at 10c+ on a wet winters day.
Even if you want to run 2 sets of tyres, I think the best all-season tyres are a better bet for UK winter use than generic full winter tyres; and the window to change your tyres over is much larger this way for optimised driving.