Sanity check..., gravity hot water and pumped radiators, should they work together

[Best]

Boiler is coming under pressure and forcing gravity flow to work, I reckon. You removing air was only a temporary sort of fix, but not correct or a solution. Get a heating engineer in to repipe the fault we mentioned and anything else they find wrong

 

[zzzjim]

..... Evidently you either don't have an export meter or have another type of feed-in agreement......

Another GOV scheme to get the ball rolling .
(Won't be wanting a Smart meter (IF it can cope !))
... Combining heat sources was expensive to do right ..(Safely)