After this thread being reignited, reminded me that I STILL needed to sort out my spare wheel void. Since I last spoke about this in 2014, I've managed to source a spare-spare wheel with an original dunlop tyre still on it, but looking rather worse for wear. I have no issues with removing this tyre to put on a modern replacement. So i bought one of these Continental ones linked previously in this thread, from 123Tyres. All in, £62.90. I should be expecting to receive this through the post tomorrow. So hopefully soon, i'll get this swapped over with the old crusty one on my spare-spare and again soon, and have a functioning biscuit (sorry - "space saver") wheel again.
Thanks for the info everyone, and the links. 8)
I heard that the old VW golf rims fitted ? But you'd need to check this out.