Many years ago most civil operators were using QFE for approach. The problem with QFE is that it is easy to forget to reset QNH on the pressure altimeter during a go around, giving terrain avoidance safety considerations. One by one the majority of UK operators had adapted to QNH approaches by the end of the nineties. All QNH altitudes are printed in bold on most approach plates and QFE heights are usually printed but ignored.
The GPWS really doesn't come in to it as one is never lower to the ground on QNH than one would be on QFE anyway. A DH of 200 feet (QFE) on an ILS becomes a DA of 460 feet (QNH) if the threshold elevation is eg 260 feet.
I've tried not to get too far in to the depths of this to save confusing you. Hope this clears it up.