Thanks to all for the comments.
At the end of 1979 Gary Hunt interviewed various space pioneers about the discoveries made in the previous decade. It was broadcast on Radio 4. My tape recording has a few wobbles at the beginning and there is a bit of a fade that lasts for a couple of minutes due to what sounds like oxide building up on the tape head! It soon returns to normal though. Some minor cuts were made by me during the recording because I was not sure that the Woolies tape would last the whole 45 minutes. Only a couple of minutes of the broadcast are missing. You can hopefully find it here: