giantjason, I work for one of the worlds leading suppliers of heating controls spares and have so since 2003 and trust me don’t take teef’s advise. As totalshell points out, the last guy who works on a gas appliance is responsible for that gas appliance so if someone does what has apparently happened to teef and something were to go wrong with his mates boiler that guy is risking a jail term and his livelihood. Treat your boiler like you would a car only if your car breaks down in the depths of winter you can’t borrow your mates boiler for an hour. Unfortunately modern boilers ain’t designed to last, believe it or not, and they really do need regular attention some brands more than others!
B.Gas, SSE and the AA all do descent well worth boiler protection schemes and I believe they all have ready access to manufactures technical fault finding. Another option is to note the make and model of your boiler and give your local plumbers merchant and see if they know of some local heating engineers who prefer to work on that brand and have loads of experience with brand. You can also ring the manufacture and ask for a list of recommended engineers in your area as using this method ensures the engineer has product knowledge if there are any issues with the boiler.
Hope this helps.