I was looking around a garden centre last week and thought I might pick up some bean plants as I hadn't planted mine. I was amazed at the price of all their vegetable plants. They were £3.50 a pack of about 8 runner bean plants! Lettuces were the same price. I didn't buy anything but went home and put my runner and French beans on damp kitchen roll, labelled them,put them into containers and placed them in the airing cupboard. On taking them out yesterday, most of them had sprouted so I potted them up. The garden centre courgette, squash, tomato, pepper, chilli and cucumber plants were £1.50 each so I am pleased I grew my own plants from seed.
I agree with Digeroo, it is not too late to grow courgettes especially if you start them off as described above, as it will give you a head start.