Autumn planting onion setts in poly tunnel

I ran out out of raised bed space for atumn planting setts, so had the idea of planting then in part of the polytunnel borders where tomatoes were growing. Had a quick google to see if it would work and found this on First Tunnels' website:

Something new to try.

 

Perhaps, but at the slightest sign they'll all get pulled up to make way for other crops, and they'll fill an empty hole

 

From "How to grow food in your polytunnel" one of my books.

Steve...

 

Can you use any Onion setts now or does it have to be some special winter variety? I have some onions from this year that I grew from seed the are pickle sized and I would like to try and grow large. I think I planted them too deeply.

 

They need to be proper sets as saved onions will go to seeds.

Checked on my autumn planted sets in the polytunnel yesterday and mice had bitten though every single shoot at ground level.