Just added the extra children's channels and they're all working well but the aspect ratios of the channels doesn't seem right on all of them. The Disney Channels and Cartoon Network all look like genuine 16:9 programmes sent as 16:9 broadcasts so all fine there. However, the others look like 4:3 transmissions of widescreen programmes, letterboxed to 14:9 and the broadcast is picked up as 16:9.
If the other channels were being broadcast as 4:3 then the picture would be 'pillarboxed' to maintain the original aspect ratio but these channels fill the screen and, in my view, it's at the expense of picture quality.
So I'm not sure if it's the channels themselves or BT who are sending the channels at the 'wrong' aspect ratio but either way it could definitely be improved.
Have you tried rebooting the STB from the power switch on the rear just to confirm its not a locally isolated issue.
BT Infinity (EASTF) 58.93/15.94 Mbps [IP Profile: 60.8/20 Mbps] using Openreach Modem & Billion BiPAC 7800N
I haven't and will give it a try. But other 4:3 content (e.g. ITV3 programmes) is showing as you'd expect.