New boiler fitted but All radiators go cold after a couple of hours??

[Junglejames]

And are the rads staying on longer?
Are the rooms heating up towards 25?

 

[transam]

Boiler plus controls

you have to love em

 

[Junglejames]

Boiler plus controls

you have to love em

Whilst this one may officially be boiler plus, it is hardly doing much.
It learns when it should come on. Oh wow.

From what I can tell, it can't fully talk to the boiler, to enable any proper load modulation (The controller isn't any good for that anyway).
My dad calls nails- 'a poor man's screw'.
What do we call this lash up?

 

[old duffer]

variable speed pump...water flow/pressure differs minute by minute...but they don't tell you that...use this to see what's happening...https://heatpumps.co.uk/heating-simulator-for-radiators/
then use this to calculate the new pipe work you need to modify to get it working again https://heatpumps.co.uk/technical/flow-rate-and-pressure-drop-simulator/