We paid somewhere between 80 and 100 euro last year, as far as I can remember. Ours is a gas boiler, and the guy that serviced it was from a gas service company. I may be being unnecessarily paranoid here, but it is worth bearing in mind that, if your boiler is gas, Bord Gais might technically require you to have the boiler serviced by someone qualified to service gas boilers, rather than a regular plumber. The "official" service guys might well be plumbers too, mind you, but a non-"official" guy may not be able to provide you with the relevant service record/document.