I think you're not far off the truth, BlueBelle. FarNorth, the other grandma and DH & I do see the grandchildren some weekends, so it's not the case that there's no contact that way. However, it would suit DD and SIL for us to see DGs sometimes during the week .. in order to take the pressure off them regarding weekends. We are all three of us happy to join in with any activities with the nanny (as we did with all the previous ones: trips to the park, school collection, playgroups etc) or to have the children all to ourselves which frees up the nanny to attend to other duties. It's simply and sadly the case that, unlike all the previous nannies, this one resents us being around at all and in any way - hence her passive aggressive behaviour in creating increasing obstacles.
Incidentally, I cannot find anything else on this subject anywhere on the internet(all discussion in any way related seems to be about using grandparents as care-givers and how to set the parameters of that), so either mine is a very unusual situation or it's a subject waiting to be looked at. In these days of more & more parents both working full time from necessity or choice (which I fully respect), it may become more of an issue .. as yet another aspect of family dynamics. The thoughtful comments posted by this wonderful Gransnet community are so helpful.
If I could persuade my daughter that I admire her for juggling family and a demanding job so well, I think that would help, but however often I tell her this, I don't think she believes me.