BigDave, I have the same problems as you when I first started G25 720 deg drifting few days back.
Starting the drift ain't difficult, but coming out from the drift/exiting the corner is the tough part. I assume the DFP wheel may not be able to rotate fast enough, so I'd suggest you to try drifting with lesser angle, just to get a better feel of the car, go slower, start your drift later than usual just so its easier to catch the slide, and end the slide.
After several rounds, you should have a better feel on how the DFP, from there you can start pushing on more and more.
It's frustrating at the start, but its possible with enough patience, a lot of focus, and practise.