DS1 (aged 5) has been a fan of Nina and the Neurons for a year or so and I think it is well made. Each week a group of 2-3 children ask a question eg how do locks work. They then come to visit Nina to solve it. There are some cartoon Neurons (who are the five senses) who help her.
I like the combination of Nina breaking down a problem in her lab with the children eg building a lock out of cardboard and then going out to see some real world examples. I think they do a pretty good job in the time of explaining and I've never seen an explanation I disagree with, though one or two where I think, "hmm, did that really fully answer the question?"
Otherwise, DS1 is now getting into David Attenborough programmes, he is watching the Africa series at present, thank goodness for iPlayer!
If you have Sky kids package there is a prog called 'finding stuff out' on the POP channel (most of the other profs on that channel are...um...not so good) but DD (aged 7) likes that one and it is very good on the science stuff.