Thanks for the reply and update! I am using my own router and the auto DNS gives 126.96.36.199 and 6.10. The DNS listed on my account settings are 188.8.131.52 & 13.50 and both set's don't enable team viewer to work.
Interesting that the Vigor 2762 is working as I guess it must be using the auto DNS.
Anyway, I will probably give plusnet a bell and see if they can solve it. As I have a workaround it's a not a issue but I am just curious as to what's blocking it.