Cross pollination

I’m hoping to save seeds from some onion shallot zebrune . 
Looks like they’re going to flower at the same time as the ornamental alliums. 
Will the cross? 

Apologies if this is a really dumb question     .

No idea, but thanks for asking as I'm endlessly confused about what crosses and what doesn't!

All I've found so far is:-
Cross pollination does depend on whether the alliums are in the same species or not. Onions and shallots will cross pollinate with each other as they are both in the species Allium cepa, but leeks are of a different species, Allium ampeloprasum, so they should be fine. If your onions and shallots are already flowering, then unfortunately, it is already too late to keep them from crossing. If one or both have not flowered yet, then (unless they're planted at least a mile apart) you have to make a choice about which variety to save seed from, and bag or dispose of the flowers of the other variety. Sorry!
https://hudsonvalleyseed.com/blogs/blog/...ollination

Thanks veggie. 
Looks like we’re all good for seed saving   . It’s just the one variety zebrune. Don’t know why I wrote it down as an onion & shallot ? Sure that’s what’s on the packet? Anyway it doesn’t matter because I just have the one variety of edible and several varieties of ornamentals about to flower.

The perennial leeks are sending up flower spikes now. Noticed them this week - and I haven't even planted out the seedlings from last year yet!

Probably not. Shallots and onions will cross as both Allium cepa but leek is Allium ampeloprasum and won't cross with onions. I doubt your ornamentals are the same species as your onions.

https://hudsonvalleyseed.com/blogs/blog/...ollination

I did notice a post from 2013 on another site, started by a guest called veggiechicken, but they have probably forgotten that by now.

The perennial leeks are sending up flower spikes now. Noticed them this week - and I haven't even planted out the seedlings from last year yet!

After harvesting one. I repotted them the next day. Poor neglect little things! I couldn’t wait till they’d died back.  They are lovely the extra space & fresher compost. No sign of flowers yet. I was looking at them this morning considering harvesting another one     .

Somethings are best forgotten, Mark.
However, somewhere I have a note of which alliums are safe to grow together because they won't cross - I've forgotten where I've put the note too.