Your employer cannot force you to take a paycut, that is illegal under the Payment of wages act 1991. Not sure if this would apply to commision/bonus payments
If they force it on you, you are entitled to resign and sue for constructive dismissal
Obviously if you don't accept and the company still has to make the savings, then there would be an increased risk if redundancy, but remember, in redudancy a company is supposed to make the role, not the individual redundant.
Note as well, if you are forced to work a 50 hour week, it's possible your employer may be in breech of the working time directive