oldbloke's mutterings

Just before we were about to leave the house this morning, I heard a fizzy/buzzy noise. Somewhere at the end of the draining board. So I moved stuff about, in case it was some object vibrating - as you do. Which revealed it was the mains switch for the central heating. Which had water on it. So the noise was slight arcing or water being boiled off the hot contacts.
I took the moutning screws for the switch plate out, and the threads seemed dry and no rush of water came out, so I'm hoping it was just condensation, but I've never noticed it happening before and even if it is condensation I don't really want it in a mains switch. My big fear is a leak somewhere like the hot water tank, with that seeping into the wiring attached to it and running all the way down... I shall have to have a good poke about in the airing cupbaord when we get home tonight (I didn't, of course, think of this nightmare scenario until we were 10 miles towards work)
Marshall's can come on Wednesday morning. We'll keep it switched off when not in use until then, and hope it doesn't go BANG when we do use it. If it does, we can try an emergency call to Marshall's and failing that the emergency plumber listed in the Yellow Pages - last time I had to call them, they charged no more than any plumber would. Or maybe I need an electrician.