I am sorry I have not replied to this sooner but it has not blooming happened since I posted!! Typical!
Green Granite, the socket on the wall where the telephone is plugged in has had to be replaced twice in the last few months due to water coming in to it from outside. Last visit the engineer replaced the entire box and filled it with tissues to soak up any water that might get in there again!!!
If this is the problem though how can it connect to my email anytime at all but not the browser when that gets stuck?
FWIW I have done a ping test and when it happens again I will do another but as I say, sods law says it won't happen now for a while!!!