Re: works both ways
If similar charges were enforcable on customer no shows ...
Oh, so you've never had to have a fault fixed then ? It's normal with every provider I've ever dealt with (and I deal with a few through work) that when the troubleshooting gets to the point in the flowchart that says "engineer visit needed" you get read a standard spiel along the lines of "If the fault turns out to be in your equipment or wiring, or if the engineer cannot gain access, then there will be a charge of £X."
So yes, they do enforce such charges : Fault in your wiring ? Charge. Tech turns up at allotted time and you aren't in ? Cancelled install or fault ticket and a charge.