OK .... I think in the light of all that, and the fact that Master O has run a further three spyware scans tonight including CCleaner and found nothing, I'm going to get a techy in from my local computer shop to have a look at it.
No, WM, the DNS servers have not reverted back, they're still at Suff's settings.
At least I feel we've all had a crack at resolving it. As they said on the Minecraft forum, there comes a time when it's probably best to get someone in ....
I'll let you know what happens.