FASVIG supports the introduction of a common UK Transition Altitude. See: VEE.10 Common UK Transition Altitude
Today the CAA has announced a consultation on the Concept of Operations for a revised UK Transition Altitude of 18,000ft.
The closing date is 24th February 2016.
The consultation can be accessed here: CAP 1349
The Commonly Asked Questions document is a good starting point for understanding some of the issues associated with a transition altitude of 18,000ft.