Onion sets this weekend?

I've had pretty good success with these the last 2 years and have been refreshing my memory on here with a bit of advice.  I don't seem to e able to find much advice in the aricles or the threads around rotation though?  What I have come across is not to get too hung up on it unless you've had problems with disease?

Anyway, does anyone know where they should go?  Is it after root crops or does it really not matter?  I grew hardly anything in the way of root crops.  Also, I put a good coating of manure over the whole plot over winter so maybe it won't matter so much anyway and they won't be reliant on nutrients left in the ground where something previously grew?

Thoughts anyone?

Just planted the whole bag where our spuds grew last year.  I'm excited to see how they will progress.  I haven't netted them but last year and year before I got away with not netting them so fingers crossed they'll be okay.  I've also put them in a bit deeper so hopefully the roots will be a bit stronger by the time the pointy bits become visible to the birds