Emily went though a similar thing too - I think it got so difficult for her carer to get her to take her day sleep even with the patting and rocking. She was just too overstimulated. In the end, as it was taking so long to get her to take a sleep and then she would be asleep when I picked her up, I thought it best to drop the sleep altogether for a while.

This worked for us as a few months later she decided she wanted to take a sleep again and would take herself off to the nursery. It then took her carer minutes to pat her to sleep instead of an hour.

Saying that if they are keeping your son up until late afternoon then he'd be way too overtired to take a nap - if however they are trying at the right times and he's not going down, maybe a new plan of action might help?