The spectrum allocation is somewhere on Ofcom's web site, I don't have the URL to hand but beware, it runs to many pages and covers almost DC to light!
As far as I'm aware, the only frequency available for use without permission is 433.920MHz with acceptable sidebands of course. In practice, I have several modules here which are locked by resonator to 433.92 but the actual transmission frequencies are as far away as 434.20MHz. These are supplied from the UK manufacturer and are not 'B' grade or copies. They use 13.56MHz resonators and PLL multipliers inside TDK5100 ICs which are also used in most similar devices.
Brian.
[Edit]
The information is on page 19 of the document "IR 2030 - UK Interface Requirements 2030 Licence Exempt Short Range Devices" from Ofcom. You need to read it in conjunction with the EN 300 220 specifications to see what category of transmission it refers to. Note that the latest release of the document is June 2014, the rules were different in earlier editions.