After many weeks of wondering why 5 updates kept showing up in the Mac App Store on my Macbook Pro I found a solution by chance.
There were 5 updates showing for apps that I have previously installed but no had uninstalled.
If I tried to update the apps as the MAS was suggesting, the updates failed. The updates would still remain. I could find no trace of the apps on my Mac until this evening.
I turns out that the apps were there but only as a Time Machine backup.
I had a thought; I unmounted and formatted the external drive that my Macbook uses for TimeMachine backups. As soon as I did this, the MAS refreshed and the apps were no more. Strange issue, but it’s fixed.