I've done less well with (specifically, peas, carrot, brussels, caulis and cabbage)
Peas I find is very much down to variety and when you sow them!
I never sow my peas insitu before June although I do fetch a few on in cell trays under glass to get an early start.
I haven't sown my main crop yet!
I am more or less the same with carrots and I haven't sown these yet either!
These will be covered with fleece their entire growing season!
The brassicas I find it is best to sow these around the end of March beginning of April in plug trays (1-2 seeds per plug)
Once they are showing the first real leaves I pot them up into 3" pots and place them in the cold frame.
I am never in a hurry to plant them out as I find they grow quite well in the cold frame then I plant out usually in early to mid May, when they just romp away!
This is also a good way to reduce the effect of club root if you have that on your plot because each plant has a good rootball by this time and can cope better with the club root.
Another thing I find with Brassicas is: I only grow F1 varieties as you more or less get what it says on the packet, so it is worth the extra expense.
Regarding netting!
Invest in in some good knitted type netting and it will last you for years I think my netting is teens of years old.
I find that once Cabbage & Sprouts are around a foot high the pigeons don't seem to bother much but it is quite different with the Caulies and Broccolies, the Pigeons will take these all the year round given the chance!
I don't always cover my fruit but if I do I wait until the flower has set and the berry is forming before I cover them until harvesting time.