What can I plant under and in hedge?

[gardenn]

Had the hedge thinned and now need to plant under and in gaps

Any ideas?

What sort of hedge? It will probably have taken a lot of nutrients anyway, but some hedge plants will be worse than others.

Which way does it face? Will it mean plants below it will be in constant shade as it cuts out the sun, or does it face the sun for part or most of the day?

Bluebells, aconites, snowdrops, anemone

Bulbs? Hellibores? Shade tolerant plants that don't need much nutrition.

In nature, honeysuckle and wild roses work.

Here is the hedge it's wild with some trees

Honeysuckle.
Good for moths and insects generally.
Smells nice.
Not precious about pruning.
Traditionally a hedgerow plant.

I know it's a lot of hard work, but I'd strip out as much of the ivy growing up the trunks and branches into it as you can possibly manage.

I'd ho with honeysuckle and roses, too, in that case, and plant spring bulbs at the base for early spring colour.

go, not ho.

Put in some wild flowers like tufted vetch, self heal and giant bellflowers. They look lovely and pollinators will appreciate them.