In this GB case that will be of interest to employers in Ireland, particularly those employing staff who sleep on the premises, an on-call night worker was not entitled to the National Minimum Wage (NMW) for all hours of the night shift; only those when he was working. Nor was he entitled to accrued holiday pay for earlier years when he was not prevented from taking, but did not ask for, annual leave.

Working time seems to be the topic de jour and this one regarding holiday credits and the application of NMW levels whilst sleeping at the place of work is very fact-sensitive. 

The Claimant was provided with free accommodation in the Studio flat with all utilities provided free of charge, together with a payment of £50 per week, rising eventually to £90 per week. In practice he was very rarely asked to assist the night care worker, although he was required to be on-call.

After a period, he fell out with the new owners, was dismissed and submitted a claim for £239,490, being the NMW from time to time since the NWMA came into force on 1 April 1999, applied to his full nightly on-call hours. He also sought some £15,000 for untaken (and un-asked for) holiday pay. 

In relation to this second factor, the EAT found the facts did not support the proposition that the Claimant was unable or unwilling to take leave due to reasons beyond his control - he just didn't ask for it and was out of time. In relation to the first element of the claim, the EAT found it was not a case where the Claimant’s attendance for work throughout the night shift was necessary in order for the Respondent to comply with its statutory obligation - there was another worker on duty for the 16 residents and all they were required to have on duty was one employee awake and the other to be sleeping. 
http://www.bailii.org/uk/cases/UKEAT/2015/0050_15_2409.html