I have kiwi alloys which I think means I have the shorter OEM wheel nuts.

What size socket fits them, is it metric or imperial?

Has anybody replaced with aftermarket solid single piece nuts and if so can anybody suggest suitable ones?

 

Should be 7/8" socket? (it is here in North America)

The sheet metal chrome caps sometimes have bulges that interfere with the socket to fully engage the full length of the wheel nut.

Pound the socket ON and then 'wiggle' off or damage the cap nut with a rod through the square drive?(done both throughout the years)

 

I used Gorilla brand. They have a smaller drive so get an appropriate tool for spare kit.
https://www.jaguarforums.com/forum/x...9/#post2600020

 

I've cut off the soft metal covers of the standard lug nuts to reveal 21mm nuts underneath them that have much harder surfaces, and gotten aftermarket slip-on caps to keep the appearance. That's one option if you're able to eventually remove them from the car, which may need a 22mm locket hammered onto each nut that doesn't want to come off.