I suggest you to browse second hand websites and eBay too, but not only in the U.K., in continental Europe too.
I saw a few Raul/Bauer come up sometimes on the german eBay. I think I even knew someone in the U.K. who recently sold his set, if I remember well.
In the U.K for instance, you can sometimes find some gems on Gumtree.com (I did sometimes at any case, and they were killing deals).
There's this one in France too :
https://www.leboncoin.fr/recherche/?text=congas&category=30You'll have to be patient and browse regularily, and maybe one day...