There is a difference between statutory holiday and contractual holiday. They will continue to be entitled to statutory holiday as long as their contract is in force, which it will be, even if they have been laid off. However, they can only receive holiday pay if they exercise that entitlement by requesting leave in accordance with company procedures.
Bear in mind that your company can refuse to allow them to take this requested leave, which is an option you may take if you are not in a position to pay annual leave at this time. In this instance, you will need to let them take it later in the year or make a payment in respect of any accrued untaken holiday on termination. As they are on lay-off and have not been dismissed, they are not entitled to a payment in lieu of any untaken accrued holidays. This can only be paid on termination.
Any entitlement to contractual holidays in a lay-off situation will be set down with their contract.