The Spa at Coworth Park

The spa sits inside a Georgian manor on 240 acres of Berkshire countryside, close enough to Heathrow that the contrast feels almost theatrical. It's the full Dorchester Collection treatment: unhurried, quietly grand, with staff who actually seem pleased to see you. The grounds border Windsor Great Park, so there's a good chance you'll spot a polo chukka on the way in, which sets the tone nicely. Vogue named it among the 100 best spas in the world.