Thanks for the tip... sadly, this one is ruled out by its 1983 date. The track I'm seeking was definitely being used on Radio One by late 1972 - it's easy to date this, as it appears very briefly in a cinema short about the radio station released in April 1973. In the clip they used, the "Memories" clip was was preceded by the famous Jimmy Castor monologue from "Troglodyte" - "what we're going to do here is go back, way back, back into time." The search continues!