Butternut Squash / Peppers / Chillis / Leeks

Squash: so long as they aare green and upright they are living, they tend not to put a lot of growth on until they decide to start to fruit, prob around august then they will grow like triffids.
Chillies: Just let them grow, I always allow mine to do whatever they want.
Cukes: It is probably still to early for them to go outside, the slightest bit of ground frost will kill them, I would aim to get them out at the back end of may and I would aim at 9 inches between each, thats what I use in the G house.
Cabbage: I transplant at the fourth propper leaf stage, I dont net but many do.
Onions: dont worry about birds, onion fly is the worst vermin, dont break any leaves around may, this is the first hatching of the fly.
Others will of course give slightly different advice but its all valid.