I am shocked at the way you were treated and yes as far as i am aware it is illegal for them to withold any references. the refrence required is the fact that you worked for that company between certain dates that is all, and not whether you got a partial fail on an ndb into x, do you have anything in writing from them saying they would withhold refrences until you paid up, and why were you bonded, they have to pay out and prove all costs and an upgrade doesnt count anyway. if i were you my friend i would collectivly invest in a good employment law lawyer cos i think by the sounds of it he would have a field day and you would get your dosh back (- lawyers fees etc) good luck, might be enough to knock a few years off your mortgage.