I've come across several recent references to the Peak District wallabies, but they died out about 10 years ago. There is a more persistent colony of wallabies on an island in Loch Lomond, conditions which can perhaps be compared to a zoo enclosure. About 5 years ago the govt estimated the UK population of red-necked wallabies to be 29, of which 28 were on the island in Loch Lomond, and the other was a fairly recent escape somewhere like Bedfordshire. I think more recently there have been a handful escaped somewhere down in the west country.