Ignoring the fact that employment laws are different on the other side of the Atlantic, Elvis, UK employers have every right to determine exactly when their employees can take their holidays. (The schools system would be in chaos if teachers were free to decide when they'd take their holidays!).
Some people might have contractual (or informal) arrangements where they can take time off whenever they like (with sufficient notice) but it's certainly not the norm.
An employer could give a Monday-to-Friday worker every other Wednesday off, plus a couple of extra days of his own choosing, while insisting that the employee attends for work on all public holidays including Christmas Day. The employee would never get more than two days off at a time, and so could never book a week away, but the law would have been complied with in full.