There were Mk1s and Mk2A-Cs mixed together pretty well throughout the Mk2s service life - the buffets/restaurants pretty well had to be Mk21
Take an example from the mid/late 80s - the Transpennine sets (Liverpool/Manchester- Hull/Cleethorpes were coach with a Mk1 CK (the only first accommodation), a brake (generally BSO) and a Mk2 TSO at each end
Take an example from the mid/late 80s - the Transpennine sets (Liverpool/Manchester- Hull/Cleethorpes were coach with a Mk1 CK (the only first accommodation), a brake (generally BSO) and a Mk2 TSO at each end