This is the style, I measure the holes at 52mm or just about 2 1/8", most aftermarket wheels seem to have much larger caps than these.....
I think those may be the "Rover factory" center caps for their "minilite" copies. They may be tough to locate.
I seem to recall having found a site that had the same size caps available, but cannot remember what the site was or how I found it before.
I think they are the same size as the factory caps, the wheels are JBW's and new Sport Pack caps are £8 each, these are just cheap plastic ones but that's all I need. On JBW's site the ones that look correct are £5 each....plus shipping of course, and again they look much nicer than these that came with the wheels.