Just to add 1 more complication. For single pilot operations in the UK the RVR minima is 800m however if you have a coupled AP then the RVR brecomes 550 (or the stated RVR) as was previously stated. However, for the DH if your A/P is approved to 200 ft you should then apply 1.25 times that ie 250 DH. So the resulting combination would be DH 250ft RVR 550M if you used a coupled A/P. A further complication is that some autopilots do not have a state minimum operating height.