airsupport
I am niether Aviator or Engineer, just the humble Ops guy getting caught up in this day in and day out, therefore, no offence is intended to either trade.
'By the way, everywhere I have ever worked the Captain can always over ride an MEL and refuse to take the aircraft, but he must have a VERY good reason and be prepared to explain his reason to the chief Pilot and Company.'
The Captain (Crew) may elect to, not accept an aircraft iaw the MEL, they do not refuse. Sorry it is a real downer of mine, the use of refuse to accept.
In declining the aircraft, the Crew will have a valid reason and thought process in doing so. This may range from the classic 'known or forecast icing' to non allowable multiple ADDs, not spotted at the outstation ADD'ing the defect they were reqested to attend.
As it is a highly trained and competant Engineer / Mechanics job to offer the aircraft iaw MEL, it is the Crew who will act as backstop, from the machine operators point of view.
A bloody minded Crew, may refuse an a/c and as you say will have tea and biccies, but I have worked for a company where engineers maintained the hangar was the base and once out of the hangar, repairs could not be made.