FTL's are the same for all UK airlines. Sharm and Hurghada are very tight on hours, unless GB intend to slip crews.
Loaded 321 depends, on your perception as to number of seats (legroom) and fully loaded. Could prove intresting in the heat of the summer.
Approx time 5:30 each way with 1hr report, 1hr turn around giving 13hrs FDP. (13:15 max)
Good luck to GB they will have to offer a good product to squeeze the IT market.