Implied right to industry standard wage?

[El D]

Hi

I've just negotiated a deal with my boss where the firm will pay for 2 years training - if I leave whilst training I pay the full cost back, the year after I qualify I pay the full back, the second year I pay back half if I leave.

Thinking about it I'm a little worried that this could be used to peg my salary back - I had a verbal confirmation from the boss that this would not happen, and I do trust the company, but if I was not on a the industry standard when I qualify would I have reasonable grounds to leave without repaying the cost of training?