Re not going to university - it's not something I take for granted. Back in the 70s when I was a teenager I think it only around 10% of the population went on to university or polytechnic or equivalent study/training, and many people didn't even stay in school long enough to do CSEs, let alone O levels or A levels. You could leave at the end of the term when you were 16, and lots did. Neil and Susan would have fallen into that demographic, and so would Mike, Betty, Eddie, Clarrie, Jolene, Wayne, Sid).
The Archers, being a bit wealthier, would have had no pressing financial reason to get their kids out of school and into a job, so they were more likely to stay on beyond minimum leaving age, and in fact David did do A levels and go to agricultural college. But even in this comparatively wealthy family he was the only one out of the four siblings to go onto HE. Kenton left at 16 and went into the Merchant Navy, Shula left at 16 and eventually scraped through professional training to be a chartered surveyor (or was it a Land Agent?), with later study to get equestrian qualifications. Elizabeth dropped out of sixth form college and later did a short marketing course.
Tony - ag coll? Jennifer - teacher training. Lilian - nothing.
Next generation - I don't think we know what James did. My hunch is he went straight into the city. John - nothing past sixth form as far as I can remember. Helen - ?HND in cheesemaking. Tom - nothing past sixth form. Adam - degree in agricultural economics. Debbie - dropped out of her degree in the second year. Kate - nothing past O level till the preposterous episode where Felpersham accepted her to do a Master's level course on the strength of a short booklet she'd plagiarised from the internet written. Alice - engineering BSc and MSc but all abandoned now so that she can be a sales rep. 
As for the young ones from poorer families, Roy and Brenda - degrees from Felpersham. Chris - qualified as a farrier after apprenticeship. Will - some sort of basic qualification in gamekeeping. Jamie Perks - training in arboriculture, last we heard. Ed - nothing. Em - a basic catering qualification. Susan wanted her to stay on at school and study, but she refused.
That spread strikes me as quite realistic. They all left school at a time when grants were available, or at any rate before fees went up and student loans became huge. Even so, they didn't all want to go into HE or meet the criteria. Lots of invisible barriers to doing that.