Start onions and spuds early in greenhouse

Hi all not sure if in right place (edible,greenhouse etc) but now I’ve got my greenhouse built been looking at getting a head start on onions and spuds early in there the over winter part is double glazed and insulated but no heater as of yet so my question is it to cold to start onion sets and first early spuds in there to transplant later when it hopefully warms up and is there anything else I could possibly start early in there or possibly a window sill in the house
Thanks all

 

Can anyone help and don’t want to waste my sets
Thanks all

 

I've put most of my onion sets in modules in my unheated greenhouse, they haven't sprouted yet and the potting compost has frozen a few times but wont do them any harm. Google 'planting onion sets in modules'. (My spring planting garlic in pots in my greenhouse are all shooting and making masses of roots).

However, all my seed potatoes are still chitting indoors as in my opinion it's still getting far too cold in my greenhouse and I still risk getting anything in there frosted. To bring some of those on earlier, I'll plant them in pots after chitting and when my heating is on, then they'll have a head start after planting out in my co0ld, wet, clay soil.

 

Thanks for that scrungee I did do a lot of research on it (google you tube etc) and although they said they can go in a cold greenhouse they didn’t mention how cold that could be I’ve only recently finished my greenhouse although not shown in pic and the winter part is double glazed and insulated but can’t afford a heater yet but thanks for putting my mind at rest

 

Got mine on the go already

 

Is that onions or pots another quick question can you start both red and white sets early

 

That's @Zigs onions thay he's got on the go.

I find red onion onion sets so prone to bolting that I wouldn't try growing more than a few in a non traditional way.