Many thanks for your detailed reply ATR.
The version I bought from the App Store is Adobe Premier Elements 11 Editor.
From what I can see it is not compatible with the version of OS X I am currently running (10.9.3 - Mavericks.)
I booted my machine up from a clone copy I made of my previous OS X installation (10.7.5 - Lion) onto which I installed my copy of Adobe Premier Elements 11 Editor when I purchased it from the App Store and it is running fine on there.
This will be my work around for now while I decide whether or not I can survive with iMovie or I need to buy PE 12 which should run on Mavericks.
Thanks again
Best Regards,
Ed