I've no idea what pihole is, so I'm guessing it's not that.
Weirdly enough, since posting this, it's all started working again. Bizarre.
In short your browser can't find the websites. Slightly longer, DNS lookup has failed. Try a different DNS service for a while (this is normally an address set on your router).
I unplugged the router for a minute, then hooked it back up. After around five minutes or so, everything started working again.
@chez_jay started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
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I've no idea what pihole is, so I'm guessing it's not that.
Weirdly enough, since posting this, it's all started working again. Bizarre.