Never an issue in South London?
In this case, changing the router mac detected new CPE, assigned a new IP and thus hadn't cached any routing. Worked around for a while.
But as for no issues in South London?
How many times in the croydon/tooting/streatham area has it failed 'intermittently' for days on end? Many!
How many times have I tried to explain to the phone handling fool at the other end that it isn't my modem, as neighbours are having exactly the same problem, only to have it suggested that their modems have obviously failed too. Also many!
Most nasty, though, was when in 2009 the blocked a whole server at the planet (hosting many, many websites, including my business sites and business sites of my clients) by IP address, because *1* URL (v1rgin dot com) was hosted there. Their excuse for the 2 week+ block (and associated lack of business? "We have to protect our branding, and it's up to the other server owner to contact us when we block them". That was from their UK head of internet security, and if that's the level of incompetence that high up, then you can see why this has failed so badly again!
Not A/C, because Virgin *really* f'd up on that one and if they want to whine at me making it even more public, let them.