Well, since posting earlier, I've been out and had a bit of a think - we have 1 DS who's 9months old, and are planning a second DC but not for a couple of years.
As it's best to plan for worst case situations, (or best, if you see it that way) I might have produced a bright child who'll get into the top uni, and therefore need to pay £12k a year, add living costs and the £50k debt levels doesn't sound stupid.
If I double that, and if I want my DCs to leave uni not massively in debt, we've got to find £100k. As I'm hoping to leave it a couple of years to have the second child, I've got a bit more time to find this money, so I think we need to save £5k a year from now. Works out at £416 a month.
I think that might be doable if we don't do things like go on holiday, replace cars, spend money on things like clothes and going out. It'll be a squeeze and a massive drop in our lifestyle, but doable.
And that would be the only savings we have, there'd be no retirement saving, no rainy day "oh shit the boiler's stopped working" fund, no 'bigger house' moving fund. I can't see we'll practically be able to live like that for the next 20 years, we will end up having to dip into it.
If every middle class family starts saving that amount, that's a hell of a lot of money being taken out of the economy. Or if every graduate starts working life paying back a massive loan, that's a hell of a lot of money taken out of the economy.
Of course, I could have produced a thick child who won't go to uni and I can spend it on a world cruise, or having a Demi Moore style total body lift in my 50's. 