What is this?

Do the leaves smell?

They look a bit like mint. I don’t know that mint has woody stems, though.

No not mint and no smell either. I can’t believe that I’ve forgotten where I took them from, I wasn’t given them and didn’t take them from someone else’s plant.

Just bumping up

Possibly a Calea ternifolia, a flowering plant from the aster family

I can't answer your question but what I do is take a photo of any unidentified plants that suddenly appear in my garden, I then use google eye which if you use google photos you'll find on the app it's extremely accurate, I also used it prior to lockdown to identify wild flowers, trees and even dog breeds.

Is it some sort of hydrangea Tanith?

It really looks like mint to me.

I tried an app I’ve got called Plantsnap.
It suggests Cornus Sanguinea (Dogwood)

It’s definitely not mint, I’ve taken a look at suggestions, and I don't think I’ve ever had any of them so thank you.
I think I’m just going to have to wait and see if it flowers at all.

I’m pleased to see that my growing in a pot Wisteria has plenty of flowers for the second year running.

The only alternative I can find is catnip. It's in the same family as catmint but doesn't have the flowers. Cats appear to find it addictive.

It looks like a runner bean

Could it be Salvia microphylla?

Looks like Philadelphus (mock orange)...