BOAC - Many thanks for taking the time in researching this issue. Today I do not appear to be having the same issues, thanks, I presume to Spyhunter [for which I paid £30 as I was so fed up with the problem] and to Avast.
Hopefully the problem is now resolved.
On a slight thread drift, when running the Spyhunter scan, after only 24 hours of using the new PC, the scan identified some 300 'spy' viruses [albeit that some of these are more to do with identifying my surfing trends, rather than anything truly malicious]. Within the time frame I had not purchased anything, visited any dubious sites etc. The question therefore, is how come my new laptop is so infected so soon. Is Dell shipping laptops with spyware already installed, or am I just unlucky?