Sorry, I am not in UK, I live in Pakistan and have learned a lot about heating systems from forums and people such as yourselves. We installed a locally made heating system in 2013 during major house renovation. The system wasn't designed properly and they put two boilers in the property; one in front and one at the back, creating two zones. The front one was way oversized for my needs (35kw) and now after calculating my property needs I have connected all radiators to this boiler which is still way oversized for 13 radiators installed at our house. I have extended pipework creating heating zones and upgraded some undersized radiators to improve the system. At some point in time I need to change the boiler to a more efficient one.
There aren't many certified or registered heating engineers or plumbers in my country of residence. Winters here are not as cold as and not as long as in UK. It gets 5degC in January and winters lasts a couple of months. It was very cold in January but the chill in air is gone in February, I think because of short duration of winters we we don;t have many qualified people here. People either use gas or electric heaters for this short duration and very few people have central heating system.