Try Smarthome. You should be able to find very cost effective switches that with an external IR receiver will be able to be controlled via the Beo5. Of course you will need to "teach" your Beo5 the necessary IR codes. I see your other posts in the Forum about programming the Beo5, so you're already part of the way there. It also occurs to me that some fire place manufacturers also sell IR switches for their units. In this case you would also have to program the specific IR code to the Beo5.
I use x-10 extensively throughout my home, but there are many more choices today than when I started. Since I do not own a Beo5 yet, I integrate my system with Lintronic in order to use my Beo4.
I recommend Smarthome b/c I have purchased from them many times over the past 15 years or so.
Good luck and let us know what you came up with.