Frantically trying to finish the book before I go away so just a quick tip. Buy chipolatas instead of standard-sized sausages and buy them loose so you can calculate exactly how many you need.
Last week, on the infamous Waitrose expedition I'm still trying to justify, I bought four decent-sized lamb and herb chipolatas for £1.22 which we had with couscous forked through with stir-fried grated courgette and a green salad. They weren't particularly nice with that unpleasant flavour of dried mint but that's another issue. (Far better to stick to plain ones)
For some reason you feel that you're getting more for your money with chipolatas than with bigger sausages even though they're thinner. They're better for children. And they're also much quicker to cook . . .
For more money-saving tips on meat take a look at the post I've just put up on Beyond Baked Beans.