Would probably recommend splitting it into two parts - although I did mine in one go with about 2.5 hrs T/O to Land. However we did the nav/diversion bit first which was generally OK but still tiring from "exam pressures" and then did GFT - all very well except after two hours or so of fairly intense work you then have to do the GFT bit in the circuit and produce your best landings - not always the easiest when you are tired.
So if I was doing it again I would probably consider two parts, but then I did pass on the single attempt so who knows really!
TZ
