In the UK the RAF specifically monitor 121.5 / 243.0 / 245.1 from either Swanwick or Prestwick Area Control Centres. This is known as D&D, who have overall executive responsibilty for aircraft emergencies in UK airspace. D&D are there to provide assistane to aircraft or other ATC units, and also facilitate aircraft practicing certain 'emergencies.'
A 'Practice Pan' is an aircraft calling the Distress & Diversion Cell (VHF 121.5) and either London or Scottish centres to practice some form of emergency. For exmple this pilot may have been practicing a diversion, so he/she called D & D to request position fixes or heading to the closest aerodrome.
Just out of curiosity, where did you fly into? Anywhere nice?