yeah we definately got to the stage where even a half hour nap meant bedtime nonsense. R seemed to be able to go for so many more hours off a short power nap. I also found the madness of NNDs settled quicker once thats all we were having. her body really did regulate much better once it realised sleep was only coming at night time.
i guess you can cap the nap and if it isn't working the childminder likely does need to accept the no napping. I mean it is going to happen eventually anyways.