Switzerland is a great option, but pricey. If it doesn't fit the budget, the French, German, Austrian or Italian Alps are all just as stunning.
DH and I also love Germany's Black Forest.
I haven't been, but Lichtenstein might be fun. Swiss-esque, but hopefully not as expensive.
In Europe, the further east you go, the further your pound will take you (generally).
What about Prague or Ljubljana?
Thermal baths in Budapest sounds luxurious.
Or get some sun and go to Split or Dubrovnik, Croatia?
Island hopping in Greece sounds great, too.