Re: Overtime payments
Actually, "Always get the offer in writing signed by someone [in management]" is all you really need.
If they are a project manager or HR manager doesn't matter. In the states at least that will be enough to get paid, and if not it will be fuel for a great lawsuit. Juries particularly don't like businesses that shaft their workforce so where the compensatory damages may be modest, the punitive damages can be quite the retirement account if invested appropriately.
I know one guy who ended up with a $2.2M payout. $200K / $2M. After taxes and such he still has 7 digits in the bank, invested such that he earns ~$50K/year just from that, and the principal still sees some dividend reinvestment.