Onion aphids

Hi I am a newby to the site, I have had a bad growing year with anything allium related due to a major infestation of onion aphids, I have found a couple of articles online mainly from Australia, I grow organically and I am looking for suggestions please. I have lost well established chives, newly planted spring onions and garlic, I am at a loss what to try having used neem tea, washing up liquid etc.

Welcome to the site 

Are they definitely aphids?  It's difficult to tell from the photos as the insects are very small, but I can't see any wings on them.  Might they be beetles?

I've not seen this sort of insect on onions before; do they wash off when harvested?  Are they actually stunting the plant's growth / damaging the plant or just on it?

  they are damaging the plants they have actually killed my well established chives that had been in the ground 3 years, i will try and get a better photo, i have 5 tubs of leeks and two of them have been decimated, they are very small beasties, when they got on my onions i thought they were beetles i just don't know!!!

I've never seen them before, but some online research does confirm that they've been found in the UK in small numbers, having been first recorded at Wisley in 1999, and are present in mainland Europe too. This article suggests they're repelled by scents such as rosemary, so that may be one organic way to deter them in future.

https://influentialpoints.com/Gallery/Neotoxoptera_formosana_onion_aphid.htm#:~:text=The%20onion%20aphid%20was%20first,cloves%20in%20a%20cold%20frame.

It does look as though that's what you've got. 

This helpsheet contains a bit more info Fact sheet - Onion aphid (276)