Wycombe, somebody has given you some duff gen. Bigger aircraft just have more inertia, so will not, initially, appear to lose speed as much as a light aircraft, but, believe me, more thrust is still required.
Just remember the diagram of forces in a turn. For the same reasons as in a light AC, so the big ones need to increase the lift to maintain level flight. We do that by increasing the angle of attack, and countering the increase in drag by adding thrust.
Pure GeeWhiz info follows: the B737-200, requires 2-4% additional N1 in a 45' bank turn, at 250 KIAS, than in level flight. (we train this at FL150, but the figures are pretty constant up to FL310)