FINALLY DNS ISSUES SOLVED
I've had similar issues, 5 months and 5 hubs later, umpteen engineers, hours and hours on the phone I finally wrote to the CEO's of BT and Openreach and copied in OFWAT.
Things started happening slowly. I won't go into the 3-week ordeal from there, but hopefully, this helps someone.
I had an OpenReach broadband engineer here today, he confirmed that the issue is not on my side nor is it on their (OpenReach) side but with BT. Loads of phone calls later (by him), they tracked down someone at BT who performed a STALE REFRESH which fixed the issue.
So basically if the DNS is not responding, chances are your settings on the BT server has gone wrong and is locked, the only way to resolve that is to have this STALE REFRESH done. Both the engineer and the chap on the phone admitted that there should be a better process in place for us the clients to reach someone who can do a stale refresh...
A more efficient and much quicker resolution to the DNS issues would be to either use Google or OpenDNS servers on all of your devices. The best thing is buy a good third party router and put your choice of DNS servers in the router. No more DNS issues. A small selection of what's available:
OpenDNS Filtered servers: DNS servers that block adult content(apparently)
You make a valid point. Things should function correctly. Unfortunately sometimes in the real world they don't always do so. Remember about IPv6 support on whatever router you decide on. Perhaps bear in mind as well the information here: