Shaun
The really serious growers grow Kelsae for show. They sow in Late November and prick out at the crook stage into small pots, grow under lights and pot on twice before planting out in polytunnels in big raised beds.
I do not have facilities to do that so I sow early Feb and transplant to the garden around the equinox, spacing at 20*20cm.
The natural life cycle of onions is a 12 month August to August, with the cold of winter necessary to develop seed heads in summer. So if you want to avoid going to seed, it may be best to wait until March before planting ou, keeping them growing indoors…..