Climb thrust setting is determined by computers and differs for many reasons, based on many factors and the pilot has no say in the automation mode of the N1 setting. This climb setting continuously varies with altitude, temperature, etc... For the pilot, he just puts the thrust levers into the climb detent when the FMA (flight mode annunciator), on the the top lines of the PFD (primary flight display), calls for it.
No, I am not with Virgin, but rather another longhaul operator.
I cannot understand why a particular airline might be slowing down. If anything it should increase, although slowly and rate of climb will degrade while the aircraft lowers the nose to accelerate, from around 10 degrees in climb to around 7*-8* for acceleration.