Ooh that’s a great trade! Can throw in a couple of chilli seedlings if you want to sweeten the deal?
Assuming you’re in London and can meet up of course(I’m in e17).
Did a cell tray of 12 onions, will do some more a bit later in spring. There’s plenty of sets in the ground already.
Another vote for starting onions in cells,(we still use egg boxes as my per my grandparents)
https://www.richardjacksonsgarden.co.uk/know-your-onions/
Also @edmundro I have a spare max/min thermometer ,happy to swap for the celery seeds.