two sides to this one - is it reasonable to take all the training costs back in one go and leave someone with nothing? No it's not
However - is it reasonable to expect someone who is leaving employment to not think about/question what happens when they leave and how the repayment is made - no
It's a hard one all round - without proper legal advice/representation - I think you'll have a job getting any other options from you previous employer.
There really isn't two sides to it. OP knew that they would settle all outstanding debt upon end of employment, and they did exactly that.
His employment has finished with them. The only means they have of recuperating the expense is by salary deduction and this was OP's final payment, thus all of the debt was recuperated.
Lets take the OP out of the equation for a second and speak generally. People just don't plan their life enough. Its the consumption driven society we have turned into. We want things now and will pay tomorrow instead of saving up then buying. I am making decisions now so that I reap the benefits in the future. I could get into great detail but I fear it will alienate. To give an example, why would you want to leave your parent's house "to get your own space" by renting? Why not stay with your parents, saving a massive deposit then have a small mortgage? The reason: life style choices, social norms and consumption lifestyle. It's all within ones own hands. You make your choices and the decisions affect you in the later years. I appreciate not everyone has these luxuries but then one should control what they can and not dismiss wise thoughts. It seems crazy to me that people have children and then can't afford. Why didn't you save up before hand? Why have the holidays, iphones and what not? One has a whole 9 months of saving up before hand and then the child comes and they're skint. You know a child will one day go to uni. You know they will once day need driving lessons. Think then plan years ahead! If you do the same thing again and again then expect a different result then you're mad! People don't want to hear this kind of thing then come up with all kinds of excuses because it just isn't fashionable or popular to think differently. THINK! SACRIFICE! PLAN! STRATEGISE! No one not the government, nor friends or family should be relied upon. Only rely on yourself and make good decisions. Always take the blame oneself for poor decisions (God know's I've made a ton). Then you will be truly in control of your destiny. One's fate is in ones own hands. Don't follow the herd. Lead the herd or be contrarian.