I suspect that the recent thunderstorms may have killed your router.
In the days of dial-up modems, a guy at PC World's Ipswich branch told me that they expected to sell between 30 and 50 replacement modems (just at that one branch) on the day after major thunderstorms. (I lost two modems that way myself!). Modern routers might be slightly better protected against current surges but they're still connected to both a phone line and to the mains supply (which makes them vulnerable). There will almost certainly be hundreds (or, more probably, thousands)of people across the UK who've found that the storms have killed their routers.
Try completely disconnecting your router (from the phone line, from its power supply and, if relevant, from its ethernet connection to your computer). Then reconnect and cross your fingers. If that doesn't work you might need to buy a new router and (using your work computer) visit the website of your ISP to find out how to configure it.
Chris