Everything about communication failure is written there in the UK AIP :
http://www.ead.eurocontrol.int/eadba...2011-04-07.pdf
Look for ENR 1.1.3 — GENERAL FLIGHT PROCEDURES
Paragraph 4.2 Radio Failure Procedures For Pilots
Here is an abstract of what they say :
(b) (i) Maintain, for a period of 7 minutes, the current speed and last assigned level or minimum safe altitude, if this higher.The period of seven minutes begins when the transponder is set to 7600 and this should be done as soon as the pilot has detected communications failure.
(ii) If failure occurs when the aircraft is following a notified departure procedure such as a Standard Instrument Departure (SID) and clearance to climb, or re-routing instructions have not been given, the procedure should be flown in accordance with the published lateral track and vertical profile, including any stepped climbs, until the last position, fix, or waypoint, published for the procedure, has been reached. Then, for that part of the period of 7 minutes that may remain, maintain the current speed and last assigned level or minimum safe altitude, if this higher.
(iii) Thereafter, adjust the speed and level in accordance with the current flight plan and continue the flight to the appropriate designated landing aid serving the destination aerodrome. Attempt to transmit position reports and altitude/flight level on the appropriate frequency when over routine reporting points.
(c) (i) If being radar vectored, or proceeding offset according to RNAV, without a specified limit, continue in accordance with ATC instructions last acknowledged for 3 minutes only and then proceed in the most direct manner possible to rejoin the current flight planned route. Pilots should ensure that they remain at, or above, the minimum safe altitude