We've had several dinners lately that consisted mainly of home-grown vegetables and herbs, e.g. a ratatouille containing home-grown courgettes, tomatoes, onions and garlic (peppers from the supermarket, alas), and I'm starting to feel that semi-self-sufficiency might be achievable next year.
There are some things we'll never self-sufficient in without a lot more space and time - peppers and tomatoes (we'd need a proper greenhouse for the quantities we like to eat), and of course maincrop potatoes - but when it comes to things like beans, root veg, brassicas, salad and herbs, you really don't need a vast space to provide two people with some fresh (or home-preserved) veg every day, all year round!