Assuming you are on a contract, a contract cannot be changed without the agreement of both parties. So they can't change your contract of employment without your agreement.
That said, they can make you redundent, but only if your position is truly no longer required. They can't make you redundant and then give your job to someone else.
Your contract might include a clause saying the company can alter your working hours as required, in which case you're screwed.
They can try to fire you for some imagined offence, but unless they've already got a disclipinary process going, that would amount to unfair dismissal.