In the 60's and 70's there were quite a few of them in the UK, but numbers steadily declined. I think the last piston Commander was probably the owner of Elstree's airfield's personal one - G-AWOE. She's still sitting there rotting somewhere, which is sad. But that aircraft had a custom radar approach system installed that was used with permission by the CAA, and probably isn't an easy conversion back to normal mode. Plus, she was very high time and probably been sitting for too long now. I don't think there are any 500B's in the UK. There are quite a few 690A/B's and 1000-models, mainly doing mapping and surveying. I can put you in contact with Mr. Richard Stanway that flies a 1000 model, M-BETS in the UK, if you want.