Basically the way it works here is the company provide you with a type rating /base check/ I/R / OPC or LPC, whatever you want to call it these days. You then sign an agreement with the Bank saying that you will pay xxx £/$ or whatever from your salary for XX years untill the Bond is payed off. At the same time the company will put the same amount of wonga into your bank account aswell, again untill the bond is payed off .
If you then decide to leave the company for pastures anew then the company stop there monthly bonus from going into your account , you then still have the agreement with the bank and therefore still end up paying for the typerating.
If you stay with the company then there isn't a problem, you keep your job and type rating is in the bag .When you decide its time to move on a few years down the line ,t hen your bond should be payed off.
This is all perfectly legal and above board.
What has been happening though is that some companies are bonding you a second or third time around , either for promotion from turboprop to jet or right seat to left seat or as in some cases they decide to move you on to a different fleet for reaons of their own. Now as far as I am aware , that is illegal, as you can only be bonded once ; otherwise they are now putting additional financial pressure on you and effectively barring you from any promotion which simply put, is against the employment laws on promotion on the UK . Same thing applies to redundant fleets, ie they trade in say, 757s for A330s , you can't be bonded again , end of story.
Best Advice is to see a lawyer . Hope this helps.