OK you asked for it, GURRYP
A rally driver contact at Rover sent me hundreds of pics a couple of years back, including quite a few of the 6R4. I don't have the original prints but...
Mid 1984 - The competition debut for the MG Metro 6R4 at the York National Rally. Tony Pond and Rob Arthur debuted the Metro 6R4 in the Yorkshire forests. This picture was taken in the 'woodyard' in the middle of Dalby forest.
Debut for the MG Metro 4R2 in mid 1984 at the York National Rally. The 4R2 is seen parked in Dalby forest the day the 6R4 was first rallied.
I don't have much information on the 4R2, or what powered it. I never realised there was such a beast until I looked through my image collection just now!