Personally would ditch BG, they are useless. I ditched them many years ago, when their "engineer" disagreed about my control valve leaking, despite me showing him the bubbles coming through a washing up liquid! Then they tried to charge me when I had a mantenance contract. I left telling them if they couldn't get the billing right, then how could they be trusted with something dangerous like gas ?
As jddevel says, find a trustworthy local guy, worth their weight in gold.
I would fit a Magnaclean filter.
https://www.screwfix.com/p/adey-cp1-03-00022-01-2-magnetic-filtration-22mm/49961?tc=WT7&ds_kid=92700038507523690&gclsrc=aw.ds&ds_rl=1241687&ds_rl=1245250&ds_rl=1249404&gclid=Cj0KCQiApbzhBRDKARIsAIvZue_O6SKJkBAt5db8pjuO1kCabiJr0hMXAex89U6ZiCivJkUgasZYb_oaArNtEALw_wcB
Easy to install and acts as a dosing point for the future. I fitted on when the new boiler was fitted, and cleaned it every 3 months until the central heating system was clean. Now I clean it annually.