Benzaah,
Thank you for the thought and I know what you mean about locking wheels making the braking seem poor but that clearly isn't my current problem as the car doesn't slow at all when the brakes are first applied. If I was locking the wheels the car would react and dip as the brakes were applied but then not slow very quickly due to the slide. I can also replicate the braking hessitation from high speed on the bench where locked wheels would be obvious.
I have a few things to try suggested by others so I'll let you know how I get on.
Cheers,
Nick
I would try more initial brake as a solution as well. I would also never bench test from full throttle to full brake unless you want to grenade a motor.