Ok hurrah, its fixed, thanks to Cartographer from DGDG.
I had so many tabs open that it was hitting the 100 connection limit and IP banning me for 10 minues. That’s why the same thing happened again when I logged onto the VPN. There must be some dapps that are opening a load of connections (DEXes, OC etc.)
At the same time my USB voltage went haywire and stopped my yubikey from working. All ok now.