Well that was interesting reading. I am involved with Emergency Planning (not LHR).
All the Emergency Responses at major UK airports should follow the ICAO annex and UK CAA CAP 168 and 576. "Aircraft Accident Imminent" is a recognised category. I have to concur with Gonzo that a Full Emergency was an appropriate response. He/she has the book to follow once the pilot has declared a PAN subject to set tech problems.
Full Emergencies happen as & when - we had two within 10 mins the other day and YES you need that Blue light response. You have to make the assumption that the Full Emergency decision has been taken by ATC for all the right reasons in understanding the difficulties being experienced by the crew - thus the emergency response is required just in case.
Question: (and I have seen the Emergency Services decide something is going to crash even though they have absolutley no new information further to the alert for a Full Emergency) - who put the "Crash" slant on this? Therefore you have to have sympathy for Notso's view that the incident was unnecessarily escalated.
Since FAM flights have been made increasingly difficult to achieve in the last 33 months or so, why on earth can't ATCO's sit in on SIM training and perhaps get a separate debrief from trainers post session. - Just a thought!