Think I'm replying to myself here. Not sure if anyone is still following this question. My situation is still that the hotkeys are deleted when the PC goes to sleep but reinstated when I reboot from scratch. Contacted Microsoft's Questions Desk for advice. First tip was to delete the hkey in the Registry, which I explained I've done with the result above; second tip - pay them either $99 or $149 to put the machine in warranty with Microsoft (it's 5 months old and in warranty with Dell - who are no good either) and they'd sort it for me. Why? Because it could be a software issue, an incompatibility or driver issue... and of course trying to fix it myself might make the problem worse. Customer service? I think not.
If anyone else is following this, perhaps you could post something soon to let others know whether it's work coming back here. Cheers