I'm afraid I didn't see the GW programme, but there's nothing magic needed - just small plants planted out after the last frosts in to a sunny spot, with a soil packed full of organic matter and well fed too. Keep the plants moist and protect with fleece in the first few weeks if night temperatures plummet. Mulch with well rotted manure and ensure they don't suffer drought stress, so that you get plenty of female flowers....and so plenty of those delicious fruits.
And no need for a grenhouse to grow courgettes - the plants, like squash, need to go out once all risk of frosts is over, but that's the only protection they need.