Thanks for the tip – you were spot on (and the eBay seller was a liar – this clearly did not work when sold!). The two drive belts are in place (but a bit loose), but the smallest belt, which I believe is how it detects the presence of a cassette, was totally degraded – it was practically liquid when touched. That would explain why it behaves as if no cassette is in place even when one is. I can get a full set of the 3 belts for £15 so will buy and replace; thanks very much for your help.
Searched YouTube and found video “Bang & Olufsen Beocord 2000 Cassette Deck – Repair, Mods, Belts & Service”, and that proved invaluable.
The eBay seller agreed to refund half the cost, so that’s something.
