Re: I'm not an expert but...
OK, so I have to admit this is what I have. Virgin 120mb/s with their box in modem mode and another router/firewall doing the heavy lifting. I also have my own DNS (& DHCP) server for resolving some stuff on the local network and pointing at Google for the rest of it. Hence I've never been subjected to Virgin's DNS issues (as far as I'm aware).
The reason I asked the question as to whether TalkTalk intercepted outgoing port 53/DNS traffic and re-routed it to their own servers is that I see that breaking a lot of things quite badly. It's bad enough not returning NXDomain when you should if someone is using your DNS servers but to intercept traffic destined for someone else's DNS servers and munging it is unforgivable.
I sincerely hope this is NOT what's happening. (I accept that it likely is not)