My connection went down this morning - by clicking various icons I was able to establish that the computer couldn't 'repair' the LAN connection and I had to 'contact my network'.
The call-centre chap from Virgin said he was going to talk me through some troubleshooting, and my eart sank. HOWEVER - the first thing he suggested worked - for now.
It was this:
turn PC off
unplug modem
reverse modem cable so that the end which was in modem is in PC and vice-versa. This apparently gives it a kick-start.
I have no idea why this has worked - or how long it will last... but people may like to know and save this info for if they have the same problem!!