I have an ambivalent relationship with Blyton myself, because the head mistress of my infants school thought her writing was of poor literary quality and banned her books from the school. The result was of course that reading them was an act of rebellion. One which was rewarded with the rather priggish attitudes of the four and the dog.
I suspect this show was too late for its own good, since the Famous Five were already old fashioned when I was a lady. The attitudes and life style tend to be of the period they were written, although I find this series is more reminiscent of old school stories than I remember the books.
Where this series succeeds is in the creation of an unreal world. It's sort of the children version of the Avengers world, because I don't think it ever really existed. Was there ever really a time when children were allowed just to go off? I doubt it, even after experiencing my own mothers ridiculous fear that something terrible was about to happen at any moment. As a child I thought the kids in Sesame Street were very sophisticated because they could play in the street - that was out because our street was a short cut between two main roads so lorries would come thundering down it. My mother then made the tactical error of getting me a bike and I was off. Definitely not overnight and while I went a lot of places which would have given her a fit, I didn't have an island or a castle to explore, sadly.
One of the things I notice about this show is that it doesn't put a foot wrong. The pace is just right, the props are perfect, it depicts England as if the 1960s never happened. Apparently if you look closely the continuty tends to fall apart, but it's wonderful escapism.