I have made further visits to the V&A with little further success, save this gem, from well outside the period of this research, about Cardew:
12th Meeting of the British Selection of International Society for Contemporary Music
10 June 1974, proposal for 1974/75
It was noted that the proposed discussions were likely to be largely political and that the three organisations involved should be advised to insist on at least some minimum performance of music. (ACB/51/272)
I wonder what the response was?