To be honest, if your loan is performing I can't see them taking anything less than what you owe them.
I owe approx €65k and asked my mortgage advisor at my local branch about getting a reduction if I was to pay off my mortgage (its also a tracker), and was basically told not to bother wasting my time, as it was too small, I was paying every week and had never missed a payment.
In your case I think offering 40 v 56 was way too low. If you had offered maybe 50 you might have got taken slightly seriously.