Can a holiday entitlement be carried over to another holiday year?

If a company provides the minimum statutory minimum of 5.6 weeks holiday, these should not be carried over.  This is because the Working Time Regulations require employees to have 5.6 weeks in a year.  Any holidays above the statutory minimum may be carried over.

However, you may want to put a time limit on when they must be taken to avoid large number of carried over days to be accrued.