Jolly, there's an explanation for the turnover of nannies: first one came when six year old was six months and DD resumed her demanding career - this lady stayed over three years and we all got on well; unfortunately she had to retire because of worsening knee problems and sadly there followed two disastrous ones (first one who was extremely unreliable and kept going off sick and then one who had to be sacked by my daughter because she turned out to have hidden mental problems which her referee had not mentioned in the reference). Interestingly, both of these nannies came through reputable agencies! During the time of these two highly unsatisfactory nannies DD became understandably extremely stressed. There were two lovely temporary nannies as well who, along with DH, me & the other grandma, held the fort during this difficult time. The current nanny has been in post for two years and I suspect that the trauma of the preceding six months is part of the reason my daughter is so worried about upsetting her. The plan is for this nanny to remain for another year, or just over, until the end of the youngest child's first term in school. The nanny does no housework, though she does cook for the children, so she will have little to do during the day once the youngest is at school, but DD is sensibly keen to avoid a changeover of primary carer at the same time as the little one starts school. She will be young for her year anyway, and won't have had the experience of full-time nursery school beforehand, as the nanny has argued my daughter into only sending her three mornings a week even though she has to pay for five.
It just seems such a shame that this younger DGC may well not see anything like as much of her grandparents (with whom she is so affectionate) during this formative childhood stage as she or we (and, I suspect also my daughter & son-in-law .. provided it doesn't impinge on other aspects of their lives) would wish.
Incidentally, I would not dare turn up unannounced. If I arrive even ten minutes before the appointed time it causes ructions.