I still think my idea was the best.
Take a number in the 147x range. If the caller dials that immediately after a call their telecoms provider credits their account with a couple of quid as a fee for taking the call (a tenner if they were TPS registered) and adds that, plus their own handling charges to the caller's bill. If the call originated from another provider they charge that provider who can then add their own handling charge and bill the caller. Extend as required until it gets onto the caller's bill or a provider who was stupid enough to accept traffic from elsewhere without having the required arrangements in place.
Yes, it would require sufficient calls to be reported against a caller to activate it, both to avoid fat finger errors and to deal with someone who decides to try to collect from all incoming calls, however innocent.
And yes, telecoms companies do know the origin of calls with fake CLI - how do you think they bill them? Come to think of it, double the payout for a call with a faked CLI.
Telecoms companies would start being more careful about who gets to set up accounts, otherwise they'd end up with a lot of unpaid bills. They'd also be faced with the up-front costs of putting the arrangement into place although the costs would be recovered through the handling charges. The consequences, of course, would be that the scourge would disappear very quickly and the telecoms companies would end up with being unable to recover those costs. However if this scheme was presented to them as a potential Transaction Handling Reimbursment in Event of Abuse of Telecoms scheme I'm quite sure they'd quickly come up with an effective alternative means of stamping out the whole thing.