i dont think a union being involved will make a big difference if the company wants to pay the government minimum, as they are not breaking any laws in paying a lower amount.

at the current rates etc - if your below 22 the amount also drops.
one of our guys has just been made redundant and his redundancy is running out 3 weeks before his 22nd birthday, so hes not getting what he thought either - which you must agree is sightly unfair in many ways!