Ah, it was the RWS 50T01 that you remember. Original Diana made rifles for the RWS ammo company which were frequently less 'frilly' than the ones they released, the RWS models had plainer stocks, no safety catches etc. I think they were for export to the US, and a few got dumped in the UK now and then. The RWS 45 had the stock from the 35, so maybe they were using them to use up parts as well.
The Original 50T01 had a very nice ambidextrous stock, however that was the best thing about it. I had one and I cannot recommend them. Get a nice Original 45 instead, by far the superior stablemate, or even one of the 'old' Original 50s or 35s.