Chainset may be a later, cheaper copy of a William's original design.
'Nicklin' made copies of the Williams C34 model from the 60's onwards, this may account for the 'N' marking on the non-drive side crank.
'Chater-Lea' dropouts were a high-end choice, I don't think Phillips used them, but not 100% sure.
Interesting markings, it seems to have two frame numbers, and that 'S' may be very significant.
'Stephens' is one manufacturer that comes to mind who built bicycles with 'Chater-Lea' rear dropouts.
I'm intrigued, more digging required.