On the 25th September (that windy day) I had a bunch of power cuts, one roughly 5 hours long presumably due to overhead cable damage. When it came back we had a few power issues but I believe those are sorted now.
The internet connection hasn't recovered fully though, I'm getting ~25ms ping times to anything beyond the router. Traceroute shows the first hop beyond me is Telehouse London and I have historically gotten around 5ms to that. I've tried different combinations of routers and modems (I tested the FRITZ!Box 7530 on its own plus my old trusty combo of an Openreach ECI modem plus ASUS router), different machines, including both WiFi and wired connections. All are the same so I can only assume it's something exchange/DSLAM end. The sync speed isn't quite what it should be either, not that it's ever been great with a 1km line.
I initially thought this would sort itself out but it's been over a week now and the single hop ping remains terrible.