I'm so glad to know that my DS isn't the only one who is dressed mostly from car boot sales (topped up by a few ebay purchases).
Funny thing is that one of our neighbours, who always seems to be arriving home with bags proclaiming that she's been buying desgner kidswear again, actually comments on who well he's dressed, when as often as not the whole outfit only cost about £1.
Even better, as they're so cheap I get him more than he strictly speaking needs, so he doesn't really wear any of them to the point that they look worn (half the beauty of buying second hand is that you can already see what lasts well so you don't get the rubbish which quickly falls apart of looks tatty). And as most things are still in great condition when he's finished with them, they can be sold afterwards on ebay or at NCT sales, usually for more than I paid for them in the first place
Like bayleaf, we get most of our toys there too - so as he doesn't really need masses of new ones at Christmas/birthdays he usually gets Premium bonds instead, which at worst aren't going to be worth any less in a few years time than they are now, unlike most toys.
Bayleaf - you sound like a woman after my own heart - perhaps now that Christmas is out of the way we should resurrect the idea of the Midlands meetup?
For other budgeting ideas, we've found that having a decent size freezer, and getting basics from the cheaper outlets like Framfoods (or Aldi/Lidl etc if they're near you) can save a fair amount compared to the cost in the major supermarkets.
Also agree with what's been said earlier about remortgaging (though personally I'd try to avoid extending the term) - and if you haven't done it lately check around for cheaper quotes on house and car insurance. If you're going on holiday, especially if it's more than once a year look at getting annual travel insurance rather than buying it with your holiday - we pay less for an annual policy than we would for a single trip!