Direct Payments for Children with Disabilities

I have 2 autistic young children.  I work part time and in the holidays their grandparents looked after them.  Due to age and illness they are unable to do this anymore.  I only work 2 days a week.   I contacted social services as I was thinking I had no option but to give work up to enable me to have them in the school holidays.   I read on a government website that direct payments help carers keep a job and would provide a carer to have them when I'm at work in the school holidays.   It would also give them more independence as they're always with me.   After meetings with the social worker at home and in their special school they awarded us 4 hours each per week every week and stated that this couldn't be saved up for the holidays? I need 20 hours per week only in school holidays.  I informed them I don't need it when the kids are in school, and asked if I could claim 20 hours just in the holidays.  They've denied this which I think is crazy considering it will actually cost the council less than they've offered us.  They've referred me back to social services.  Has anyone else had issues with direct payments?