@Rom: I'm not a clip-board-waving safety freak and my post was not aimed specifically at you! We get a hell of a lot of ppl posting on here about removing the cover from their room sealed boilers and then the RGIs on here post back that they shouldn't! I just wanted to go a bit further than the 'rules are rules' standpoint.
As for your motoring analogy, I get your point but... by law, a vehicle has to have an MOT safety and road worthiness check every year... a boiler doesn't (unless you're a landlord). So, some installs we attend may not have had professional attention for many years!