Well - on the seeds front

Generally if you plant seeds in a straight line you can usually tell which are seedlings and which are weeds as the seedlings should all look the same and be in a straight line. Parsnips are notorious for taking a long time to germinate. You should leave 'weeding' until you are sure which are seedlings and which are weeds. The weeds generally grow more vigorously!

I can't envisage what sort of plastic loses its coating so I can't help you there. You could ask your neighbour in a nice friendly way - kind of broach the subject whilst you are having a general chat about growing things etc , rather mentioning it straight away. They might not realise that it is shedding itself all over your plot and might do somthing about it.

Netting - hmm. I scare the birds off with cd's on string tied onto sticks - it seems to do the trick for me and we get lots of birds and pheasants. The cd's are free ones you get in the post of giveaways in shops. The birds do not like the noise or movement or the flashing in the sunlight.

I use old bits of things to make a net cover for low growing things if I have too. Not very attractive though - bits of plastic water pipe, conduit, bits of metal, sticks, canes, that sort of thing. But my site is in a big field in the countryside so well all 'make do and mend' but I don't know if you can do that in town sites that are all nicely paved etc.