Michael, it is is a good thing that you are rated. It's actually 15 or 17k for the rating depending on fleet. It's an upfront payment too. Company then pays you back over 3 years. It's not a bond in the true sense of the word.
Best of luck.
That's certainly how it was when I joined 4 years ago. I thought long and hard about paying over £15,000. I asked the then HR manager if the funds were held in an escrow account, and received a somewhat snappy answer of 'No'. The funds go into the company coffers without protection. I looked next very closely at the company accounts, forecasts and history and took a calculated risk. I got all my money back and with interest (in pure financial terms not a great investment return, but in wider terms of knowledge and experience, a priceless return). I'm not sure I would calculate the financial risk the same way now with the company in strife over publicity and having even been discussed in Scottish Parliament. It's a lot of money to buy an entry level job (salary comment).