And @Sharkstar too.
After a bit of a think I arrived back to the point we were at last time I had boiler chat 2 years ago. It's not worth it for us. Rad control would be rad but pricey.
Also, when we spoke to the installation duder they said "yeah, I only have it because it's shiny gadget"
Tempted by the vaillant specific boiler controller. If only for the better programming and the ability to turn it off when (if right now) we're out and about.