I was under the impression that a Type A RCD was the minimum you could use (although Type B is the prefered device).
Different Type RCD’s have different characteristics and depending what its for. The well known RCD for many years is the Type B, which is classed as Type AC. Have a read here for a better explanation-
The problem with MCS is it was easy for someone with a bit of cash, to go on the course, with no experience what so ever as a sparky (PV) or Heating Engineer (HP), pass the course, sign up to a regulatory body and get basic liability insurance and then be let loose on customers premises and soon go out of business and restart up again or in something else. I could go on, but you get my jist and the likes of Brydo on here no all to well of the consequences.
When you eventually have PV, its essential to do your homework to a persons background and how long they have been in the electrical industry and also to ensure you get an insurance backed guarantee, as your covered for crap or if they go out of business.
The joys of the domestic sector has never interested me lol.