In previous years I have occasionally sown a second wave of courgettes which have done well after the first wave has given up the ghost - but I can't remember when I did it. Have I left it too late this year?
I wouldn't start off any winter squashes, of course, as they need time to grow and ripen and harden off.
I have often found it a good idea to have a few late ones once the main crop are rather straggly, I have found I can get an extra couple of weeks by cloching up. Thanks for the reminder I have plenty of spare seeds, worth giving it a go.