Is your other one from the early 80s with the silver chassis and black engine cover and chrome wheel caps with black centres? I have that model too as well as the auto drive you have pictured. Both of mine have no catcher and have things wrong with them. No auto drive system on the older one and busted cable and engine seal on the other! Believe me, bits are getting hard to come by for these classics in oz as well but admittedly you do see complete auto drives in various states on eBay sometimes, but never with the auto drive specific catcher! We exported shiploads of the VC series to the UK at the time didn't we? I wouldn't be surprised if close to the same amount were sold there as in their home market. I'm sure there are a few barns and sheds in that vastly populated island of yours with the stuff you require. One advantage you have is your country is smaller and if you were to discover someone has a bit you need, chances are, it will be within a drivable distance, unlike here in Oz where the distances are too great to collect a mower that is interstate.
Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!