ID? 60's/70's chair  

Arkana
possibly?
( I assume they're in the UK?)

.
I've not seen these before (they'd be remembered, wouldn't they?) but my 1st thought was Pieff - they used a very similar 'foot' in the Eleganza range. Hope you get a result...
Claire

Yes
Pieff is another good contender, assuming they're UK made.

And then I looked again...
and I thought that they reminded me very strongly of my Z Down chair by Erik Magnussen - for Englebrechts I think I remember(NOT my favourite chair but my toddler has bitten it, so teeth marks and all I think we're saddled with it)
I think there are lots of similarities and they may well be related.

Not necc UK
Thanks for the suggestions. These chairs were bought in the UK but could be from anywhere.

Yes
I/we realise they could be from anywhere, but from a lot of experience here helping people identify their things, the country of purchase is usually a good starting point for identification.
I wonder if they were possibly 'upscaled' with cheaper cloth or canvas seats being replaced with leather?