I love the UK, so wouldn’t really look to move away. However;
1) Due to fortunate personal circumstances Italy is the most likely place I would end up living. It’s beautiful and the South where I would be has a good lifestyle, cheap cost of living and cool, cheap trains. However, there are downsides; I think winter there would still be pretty miserable as the houses there are tiled to stay cool in summer, so it’s not as cosy as being in the UK, Southern Italy also has its fair share of issues just below the surface and there are many things that I would miss about life in the UK.
2) More speculatively; I’ve visited 38 countries now and there’s only one that’s really jumped out at me as somewhere that I could happily live year round, and seems pretty flawless, and that’s Canada. It’s like a friendly more sensible US, is beautiful and has clearly defined and spectacular seasons. I might miss rail travel though as the network there isn’t developed to the same extent as here.
3) Sweden, similar to above really but with less conviction. It came across as a really nice and beautiful place. Many people speak English so that helps.