BG wouldn't go near it without any service history let alone the age of the thing. "They said it looked five years old" LoL, they'd know it wasn't let alone finding parts for the thing. BG start panicking with eight year old boilers, this enquiry stinks like a DIY effort gone wrong or perhaps more likely somebody was employed who wasn't qualified.
Trying to bring peace between various parties on this thread, who knows which cover wasn't replaced. In fairness, BG hasn't always been above criticism, so we'll never really know, but sometimes faults do seem to come in strings.
It is of course possible that whatever caused the old PCP to fail has also strained other components, or that the PCB failed in a mode that did so. Unfortunately, the good advice that can be given on this forum already has been, as we cannot start discussing boiler repair techniques on an open forum.
Best I can suggest is that the OP finds another Gas Safe registered installer for a second opinion if she or he is unhappy with the service BG has provided. If the OP gives the location, there may be someone on here who may be local to them.