Changes to working hours

Ella_fella

So I currently work a 3 on 3 off rotating days and nights shift pattern. My current employer called all staff into a meeting yesterday to say that the business was implementing a new shift pattern either in a week's time or two weeks depending on the majority who voted for either. We were all then made to sign a piece of paper saying that we had agreed to this change. The staff are all monthly paid so not sure what notice was needed to be given for a change in working hours or whether this right has now gone out of the window as we all signed this document!
The next part is the pattern itself, we all work 8 hours a day instead of 12 but the first rotation is starting on a Sunday morning shift 6 am until 2 pm then all the way through to Saturday inclusive then the next day Sunday working a 10 until 6 Nightshift all the way through until Saturday morning. That's 14 consecutive days that we will be at work for by my reckoning - is this legal?