Got it working and the guide was 99% right. Draytek did a remote access and after a bit of confusion as to why things suddenly stopped working part of the problem was that lan dns needed adding.For some reason when traffic was directed down one wan the internet traffic stopped as the wan dns wasn't being picked up. Strange.
The issue with BT youview box was that it needed bt's dns entries entering manually otherwise it couldn't see the stream channels. Enabling that still left the 4k stream stuttering. I may have fixed this by telnetting in and enabling igmp snooping the turning of txquery v3 and also ensuring that igmp proxy was set to v2. I noticed the vigor 130 was V2.
Fingers crossed it will stay working. It did work for 20 minutes earlier in the day after my first play with telnet.
Also had to create a rule to stop the traffic being switched from Virgin to BT for no reason despite the wan speeds being entered correctly. This maybe due to Virgin capping single thread and the router thinking the speed was lower than the BT line. Just guessing there.
I then tidied up the routing by creating ipobjects and groups.