Maybe the age difference explains the reason behind the bond - maybe they paid for their own ratings? But let's face it, we are big boys (or girls) now and we do have a choice when confronted with a bond. You agree, your problem! As for the legal side, I'm sure your Balpa rep will explain - you are a member aren't you?
But a few final points. Firstly, well done in not paying for a rating. There are too many people who do and it does the "group cause" no good at all. Secondly, it's only fair that your employer gets a return on their training investment and lastly, to jump ship with less than a few year's experience and 1,500 hours on type might not be your wisest move.