There was a good thread on this in ditto.com but it's disappeared into the locked chest that was the old Knapp's Office.
PLC (or PLT) has been popping up in this country from time to time but no one has managed to stay the distance. Plenty of info via Google:
http://www.google.co.uk/search?q=pow...UK%7CcountryGB
One of the big issues with this technology is the interference that it will cause to other services. The beeb, in particular, are not at all impressed:
http://www.bbc.co.uk/rd/pubs/papers/
See under Spectrum Management.