TPS have a say over residential lines, but you cant register a business line with them.
TPS will take action if you have the callers details inside the UK, but if they call from anywhere else they have no power to block / take action.
Most of the time out of UK call centres will place an invalid outgoing cli so they cant be identified. Example cli "50776" unfortunatly this is so easy to do with a digital trunk or even an ISDN 2 line.
AFAIK.