One of the attributes of a good atco is someone who has the tenacity to change a difficult scenario around and fix it, without chucking the headset on the floor and walking away. The very fact that you are exhibiting this trait is a good sign. Its a fact of life that many promising cadets don't fit into what the NATS college are trying to mould them into in the allocated amount of time, so put your experience at Hurn behind you and look forward.
If you are contemplating funding yourself through an ADI course, why not give the Principals at either of the two available colleges a call and ask them how many of the people who had passed their ADI course either gained employment or were picked up by ANSPs and sponsored through the APP course and onto a position at a unit. You might consider it is worth the risk.