Thanks to Smoggy, I should have my Union Jack side marker options soon. I tried to order these from a UK seller but they won't ship to USA. So Smoggy was kind enough to get them for me and after some trading/swapping parts, they're on the way. He sent me a photo of it beside the side markers on his XK8 so I think once I trim it down to fit in the chrome lit marker trim rings, it should look great!
I may have my trim guy cut a silver sign strip to run through the horizontal stripe with the jaguar logo cut out. Similar to the wheel badges.