There's good news and bad news:
The good news is that I did record it when it was shown on BBC4. The show was "Steeleye Span at Penshurst Place", originally screened in 1974. John Watcham and the Albions perform Upton Stick at approx. 18 minutes through the half-hour programme.
The bad news is that it's recorded on a DVD-RAM disc, which won't play in most DVD players or computers. My only excuse is that I plumped for a DVD-RAM machine so that I could edit what I'd recorded (primarily removing the ads from C4 films).
If you have a player that can handle the format, Steve, you're welcome to borrow the disc. Alternatively, if anyone knows of a techy solution, then please let me know!