I found the problem.

Instead of deleting this post I will leave this up so that if it happens to anyone else they know how to fix it.

The controller was at fault and not the picooz helicopter.

After I took apart the controller I realised that the throttle circuit board contacts had 'ripped' somehow. Basically a bit of the circuit board foil had come loose and was shorting the heli to full throttle when the stick was at idle.

I had to remove the throttle mechanism, take it apart and clean the contacts by wiping off the pieces of broken foil. I also bent one contact half a mm to make sure that it was going to work as it looked as if that was where the foil had ripped from.

For more info send me a message and I can explain further.

I removed the throttle spring at the same time and find that flying altitude wise is much easier now. Everything works fine.

Take Care