@d-healey Thanks David..... Flushed with success I'm downloading the tutorials now to dig deeper....

I may have found the answer!
Just tried again, starting from scratch as far as saving as a preset, but then this time instead of loading the project (step 2 in the reload as work in progress section) after restarting HISE, I simply opened the .hip file without doing anything else, and there was my project as I had left it, with working sound from mouse and midi keyboard.
It seems that the 'Load Project' option under Files is not necessary and indeed stuffs up the sound from the project - all that is required is to load the .hip preset file.....
It takes a while to get used to the terminology used - I had assumed that loading a project would re-load a previously closed project in the state that it was when closed, but obviously not so. So really the preset is a backup of the project at a certain state and if I want to go back to a selected point in the project development, as long as I have saved a preset at that point (with a suitable name) I just need to load that particular preset.
Now I'll continue with the tutorial, saving a preset at various stages and see what happens when I restore from each.....