Ben responded within minutes to the initial mybuilder request, kindly offering to come along at short notice (later that same afternoon / early evening after he finished another job in the area) to check over the boiler and issue the gas safety certificate requested at similarly short notice by my property's impending buyers. Although such was not legally required, I didn't want to faff about and risk the sale being unnecessarily delayed!
I can commend Ben for his responsiveness and workmanship on this one. Recommended. :)