One of the reasons why it's been so popular is precisely because the family is typical of vast numbers of middle-class households
if you drive through the leafier 'inner' suburbs of south, north, west London (don't know about east, it's a foreign country!) you'll find street after street of houses just like the Outnumbered house, and the same goes for Bristol, Manchester, Birmingham etc etc
There are millions of families like that all over the country - not particularly well-off but not cash-strapped, parenting skills are well-meaning but a bit ineffectual, concerned about education, usually voted Labour but possibly flirted with DC and/or the Lib Dems last time round, trying to juggle jobs & family and dropping a few balls while they're at it - I'd imagine a substantial tranche of MNers are like that ...
Yes, it's definitely past its sell-by date, mainly because the children are now too old to get away with the mix of innocence and knowingness, but not because it's not typical ...