From the UK AIP, ENR 1.7 Altimeter Setting Procedures:
5.3.1 When an aircraft is descended from a Flight Level to an Altitude preparatory to commencing approach for landing, ATC will pass the appropriate aerodrome QNH. In addition, ATC will also pass the Transition Level in due time prior to reaching it during descent either by voice communications, ATIS broadcast or if available, data link. On vacating the Flight Level, the pilot will change to the aerodrome QNH unless further Flight Level vacating reports have been requested by ATC, in which case, the aerodrome QNH will be set following the final Flight Level vacating report. Thereafter, the pilot will continue to fly on the aerodrome QNH until established on final approach. When requested by the pilot or local procedures require, the appropriate QFE and aerodrome or threshold elevation shall also be given.