That's just jogged my memory, the O2 router isn't very good when there is Lightening about. Mine messed up twice last month. I had to use the pin hole reset button at the back of the router.
First time it happened I couldn't load any web pages but I did have a connection to the exchange the following week I had to do it again after another storm, I don't remember what went wrong but it wasn't the same fault as before.