After 90 mins in all, with Pipex & their support in Port Said & Scotland, eventually found that it was due to the basic settings on our Netgear slipping out of kilter.
Just as well, therefore, to have ones settings noted down so that they can be checked, witout assistance, in time of trouble?
An easy way to do this is to copy the "open" window (the one with the dark blue at the top) by clicking alt+print screen. Then open Word or whatever you use, and paste it onto the document. You can then add comments or instructions etc.
I've done this for all my settings, and were extremely helpful a couple of weeks ago when our connection kept dropping out - we had the printout of all the settings there to check against what was on the screen and were able to confirm that the problem was not the router, not our settings, not Pipex but dear old BT. (Again)