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Thanks Craftypig for your very quick reply and thanks Albags.
Albags, I did exactly what you suggested and found 3 trojans with Housecall and 15 problems running Malwarebytes. All now saying clear. However since I logged back on AB I have had 3 chances to win something, one saying I'm the 1,000,000 visitor I could possibly be the winner of a mercedes. I can't remember if use to get these or if I'm paranoid and now notice everything,which I previously just ignored, or if my pop up problem hasn't been resolved.
Back button still taking a few clicks so that must be something totally different. Have you any more ideas please ?