Now, heres a strange thing.......!!
I had been saving all the plastic trays that food comes in with the intention of using them as seed trays. I had amassed quite a few in the last year.
anyway, i was sowing various seeds this year - mostly my chillis, peppers and toms.
Anyway, the ones in the "traditional" seed trays germinated with reasonable success rates however, the ones in the "food trays" did nothing!
I put several drainage holes in them, they were filled with the same compost and watered in the same routine and heated to the same extent - but did nothing!!!
So, i'm sticking to my seed trays in future.
I think using the plastic bottle idea would be a good way to protect and start off Onion/Shallot sets - birds like to pull them out the ground and if there is a lot of unexpected rain, the sets can rot, so placing a plastic bottle over them should help to give them a good start. i've jsut planted some more onion sets, so i think i'll give it a go myself and see if they turn out better/worse than normal onions.