I started MathPhys this year and we do labs in the third year, so you shouldn't be completely sunk if that's what you want to do. It's true that straight Phys do much more of it, though. Also, this is anecdotal and maybe not very helpful, but my personal statement didn't mention maths at all (since I was applying for regular Physics elsewhere), so I don't think they mind. The course is run by the Physics department, anyway.