If the flight to Dalkeith was tasked after takeoff on the original sortie, the pilot would presumably have to assess the feasibility of the request from a fuel perspective "on the hoof" so to speak?
The initial task in the local area would not have presented any challenges from a fuel perspective, but factoring in a trip to Dalkeith would have taken them much further towards the edge of the fuel envelope. 10 minutes on task at Dalkeith doesn't seem very long, although I acknowledge the effectiveness of the helicopter in many situations, so I guess it could have achieved whatever its objective was in this time.
If the decision to fly to Dalkeith was marginal, and if the fuel contents monitoring systems were suffering from the fault subsequenly found on other airframes, the advent of the red "final warning" light with no prior amber warnings over central Glasgow would have been a nasty shock to say the least, and would presumably have presented a terrible dilemma: park the aircraft somewhere very high profile and sub optimal, or try for home.
Quite a number of "ifs" and presumptions I know, and hence just an attempt to try to string the evidence together rather than point any finger.