I cannot edit my original post so will update here.
It appears to be an issue with DNS. I have a dynamic IP which is using a DynDNS service and my domain A record was pointing at that which has worked for more than a decade.
I pointed the BQM at the dynDNS entry directly and it is working fine again so could be the providers DNS playing up (123-reg).
OPNSense
PiHole
Unifi for Wifi