Farfrompuken,
I wasn't trying to "kill the messenger" but I still have a special place in my heart for the RAF TriStars, I was the Lockheed "on-site-represenative" several years ago and have been hearing what bad shape the TriStars are in since before I even got to Brize Norton. The people of he 216 Squadron do a great job of taking care of the day to day problems, but having to relay on Marshall and Gamco (or what ever they call themselves now) for the heavy maintenance just takes too much time and money.
IMHO you have hit upon the reason the RAF has so many problems with the TriStars is that they don't use them as they were intended. Far too time much sitting on the ground and not in the air.
Cheers!