Question Author
Thank you all for your comments but also please accept my apologies because the position I described was not quite correct.
The first scan was in fact with the free Avast which was already installed and it was this that showed the Wannacry message. I ran Malwarebytes which showed it to be clean.
I then ran PC Protect which showed a different virus plus a dozen or so unwanted programmes but no Wannacry. I then ran Malwarebytes again which showed only the PC Protect entries.
I have now quarantined the lot, uninstalled PC Protect and Avast and hope that might be the end of it.
Thanks again