Hi there!
You are right, in that a BA 3 day trip is out on day one return night of day two and arrive day three. All BA flights are timed in GMT/UTC/Zulu whatever you want to call it, and they take into account the legal amounts of rest needed. It works keeping everything rostered in one time zone as there are many variable zones including 1/2 hours!! So if the rostered everything in "local" times it would be confusing.
As regards to your choices between QFUK and BA mid fleet there is no longer a BA Mid fleet. I presume you are referring to the "single fleet" at Gatwick. This fleet will offer the opportunity to do a mix of shorthaul and longhaul flying. The Shorthaul side is very work intense: upto 4 sectors per day. The longhaul will probably involve 2 sector night stops on some Caribbean routes and possibly 1 sector extended (ie 2 local nights) destinations.
Apparently the new fleet at Gatwick is being classed as BA mainline however the opportunity to transfer to Heathrow (s/h or l/h) may take a very very long while. There is also the possibilty of being able to bid for your work as currently on Gatwick E/f but how that will encompass the longhaulside remains to be decided .
Hope this helps if you need more info PM me
