I work for a small charity which offer after school care and Holiday Clubs for children with Special Needs. Most workers have contracts for the After School Care and Holiday Clubs is classed, I think, as extra hours. Up till now, holiday payments have been based on their "contracted" hours, i.e. hours worked in Holiday Clubs is ignored in the holiday pay calculation. Surely this isn't correct?
Depends what else they do and how much holiday they have - the minimum is 28 days (including bank holidays) for a full time worker here. I they work more than 5 days they do not have to have any additional holiday. Part-time is pro-rated. You can, of course, offer more.
Holiday is based on contracted hours, not overtime, unless contracted hours are genuinely completely flexible in which case it should be calculated on the basis of 12.07% of hours actually worked.
If these workers regularly work the holiday clubs as well as after school, are expected to do so and expecting to do so, it's possible those are contractual hours. Is there a reason they only have contracts for the after school?
Well I think it's unlikely, but yes they could be working in excess of 5 days a week, but that still doesn't make your point relevant to the OP's question, which is what I said.
The OP wanted to know whether holiday is calculated based on the after school hours in their contracts, or the increased hours they work during holiday time.
As I said, holiday is based on contracted hours not overtime, the exception being where hours are very variable, in which case the percentage calculation should be used. The other relevant point being that if those increased hours have become contractual, the holiday would be based on those hours.
And yes, workers who are contracted to work full time (regardless of whether full time means more than 5 days a week) get 28 days. As I already said.