The Julian Wiseman site contains a version of JSW2+ that as mentioned in comments somewhere. Contains a problem with being able to escape from the "Off licence" in the end game sequence. As a result of that problem, it was decided to continue the development of the game. The final version is version +E22. Which has around 298 objects to collect, and 145 rooms. In version +e22 the game starts with the title loader screen from JSW2.
The game was edited up to the end of 2016. And every version was just a test platform, to see how much could be added to a standard 48k spectrum.
Posted the latest version +ve22 on this website in downloads
Jet Set Willy And Manic Miner Community
? Downloads
? Jet Set Willy
? Jet Set Willy [Third Party]
? JSW+ Ve22 rv1