Deadly silence from draytek. Sadly don't hold much hope since they hadn't clue last time.

Got a useless reply from Draytek from someone who doesn't seem to know basic fault finding.

He also offered poor advice over the firewall by saying disabling it doesn't disable the dos as these are separate. Well according to the manual disabling the firewall should turn it off. However it doesn't seem to be doing this and neither does manually setting them to disabled I still get the flood message. Interestingly I telneted in and toggled the firewall on and off and the status seemed to stay the same.

After a polite explanation of how to do trouble shooting and why I rolled back to previous known working system including resetting the defaults before loading the backed up config got a better response from draytek. They confirmed that part of the DOS isn't configurable by the web gui and still remains active despite turning the firewall off. Bad programming by Draytek as off should be off.
Sadly the suggested work around didn't work and I'm beginning to think that the 2960 can't handle 4k streaming due to software constraints. I also reckon bt have changed something.

As a test I'll put my old draytek back on the bT line and see if that still works if it doesn't then I know BT have changed something if it does I know it's an issue wiotht he 2960 and then it's a case of finding one that does dual wan and can handle 4k streaming. It will also need to handle 500 or more nat through put as well to allow for future speed increases. I use virgin as well.

My old draytek works without issues so we are back to an issue with the 2960. Whether they can fix the issue is another matter.

Your explanation here is unclear and rambling (to me, personally) so hopefully it's clearer to DrayTek support

A clear concise explanation, always stating version numbers would help.

Draytek will do a remote session tonight.
Hopefully they'll get the 4k streaming to work again.
I'll back it up first just in case they break something else.