We have a product here that emits a tone everytime you pick up the phone that sounds like your line is disconnected. It only emits the tone for a moment, then the call resumes as normal. I guess that telemarketing software detects this tone and ends the call before you say "hello". Best yet, they usually remove you from their call list automatically. Called a "telezapper" or something. Do they offer a product like that in the UK? Would it work?