I seemed to have solved this issue for me.
Problem was Suitcase Fusion 7 (old unsupported version). I noticed that it would activate fonts and then de-activate them after a second or so, after a search I found an article form Extensis that that was titled something along the lines of 'Suitcase no longer activates fonts after upgrade to Windows 10'. Whilst the article itself was no longer on thier server, I went ahead and uninstalled Sutcase and now all 3 programs open, font previews are good, font selection is correct, so essentially no problems. I guess I'll need to upgrade to a current version of Suicase (assuming that works correctly with Affinity apps - can anybody confirm?). I'll also need to do this to my desktop PC as it was exibiting the exact same problems.
Mike