Tested the work computer again today and the same thing definitely happens there, so it's not limited to my home network. Is it a coincidence that my work email address has started receiving 30-40 spam emails a day when it has had none for five years?
Macster: Apple-K does nothing on my mac.
Keef: I'll give the Firefox Adblcok a try and see if it makes any difference.
thanks all.