I think the confusion might be a mix up with an earlier MBT LZ293, which had the earlier scheme and without D-Day stripes. Photos of this bird also have the black appearing engine rings.
The only reference I could find was in Norman Franks' Fighter Commands Air War 1941.
Essentially a Gudgeon operation was a Circus but with fighters from 10 Group. I gather the parlance was dropped in favour of a dedicated Circus number as things got more co-ordinated. This was early days for fighter command and its organisation of fighter sweeps over France. There was quite a lot of changes in organisation and tactics as things developed.
Does this fit in with your question about 316 squadron?
Jan Zurakowski described the MB-5 as the best aircraft he had ever flown. The trouble was by that time there were other types that had just as good performance that were already in production.
I would love to see a model of a MB-5 Dave, is that next?
Looking around on the net on this subject I found and example of a pilot doing 14 ops in 26 days. I suppose on Maximum effort periods the aircraft few every night until unservicable, though not necessarily with the same crew.
RCM is Radio CounterMeasures . The Halifaxes would have been part of 100 Group involved in jamming operations of radio frequencies used for fighter direction. Search for AirbourneCigar (Usually referred to as ABC), or Jostle.