Is there any reason you want to replace them? As long as they are above the minimum thickness cast into the rotor it's fine. No vibration when you apply brakes? No scoring deep enough to catch your fingernail? Then there should be no need.
Across the pond here in the States Raybestos "red-label" service grade rotor (or Raymold brand) around $15-20 USD is fine. If you need to spend more than that, the next step is pretty much around $40-50 USD, and in most cases we can get best-in-class Brembo.
On some model years there isn't Brembo available, Raybestos Advanced Technology rotor is another good choice. You may have Forodo or something like that in the UK, which Range Rovers use. At least the pads are. These are made by TRW automotive. Should be good too. If not maybe ATE by Conti?