I think this series may highlight the dangers of production teams assuming their show is going to run for a second series. If you like your shows tied up with a bow, you will be disappointed at a few of the story lines remaining open when the show was cancelled.
Having said that, I don't see this show as being as wonderful or as terrible as a few reviews I read led me to believe. Yes, it is a period soap opera with dramatic stories in the same way Downton Abbey is these days, though admittedly not with the same quality of writing or perhaps even acting. Still, I think show does okay at least, given the overall decline of television offerings and influx of (so called) reality shows and poor-taste sitcoms.
The series follows three new nannies in a fashionable district of London as their stories and problems intertwine and expand and contract. We meet a lot of lesser characters which complicates the story somewhat, but I didn't find I had much trouble keeping track of it all. There were a few subplots that didn't seem to add a lot to the show in the long run, but it felt like they were done to give characters more of a focus and make them less one-sided.
If you like period dramas and need something to watch until the next great one comes along, this one will keep you in the game, so to speak.