Is this some sort of celandine?

Cyclamen?

 

The leaves aren't as thick as cyclamen @SherwoodArrow . It would've been nice, though.

 

Yes I think they probably are ...

 

You do get variation in foliage of celandine, I found one a couple of years ago with very dark leaves.

 

Celandine and there are a lot of ones with names where the foliage is non standard.
There are different shades of yellow, orange and even white. Also doubles and a green flowered one too. Try counting the petals on any you see, there are ones with 8 petals and others with ten

 

@Palustris I'll wait for it to flower. It's wedged itself between a geranium and a veronica. If it behaves like the lesser jobs, it's unlikely to do any harm.