Annobel, I don't live near them. I live about 2 hours away by train. It's not that I'm single-handedly cleaning the house for them -- sorry if I gave that impression. They do manage without me most of the time, it's just that when I'm there, they don't seem to view it as an opportunity for their children to spend time with their (other) grandmother, they see it as an extra pair of hands to help out with the chores. (Or so it seems to me.)
I helped a lot when the first was born, and was only too happy to do so, as my daughter-in-law had a bad time and besides he was my first grandchild and I was over the moon. But as the months rolled on, and the baby got older, I still kept being called down to help, often at very short notice and for things which seemed to me quite minor, such as for instance if the parents both got a tummy bug or a cold. And when I was called down, I felt as if I was treated more or less as an au pair might be treated. I don't want to go into too much detail, because I know my daughter-in-law uses mumsnet and I don't want her to read this and recognize the situation. But sometimes it was really over the top, and I wouldn't have stood for it from anyone else.
I went down less and less, making excuses sometimes, and this was noticed, so that a certain froideur crept into our relationship. When the second baby came I didn't see much of him at all. But he is a lovely baby, they both are, and thriving and happy. That's the main thing.