I got a Low Coolant warning last week on my XK8. I stopped and checked the coolant and all was well. Later I checked the coolant level sensor and it was bad. open circuit with or without a magnet next to it.
I decided to give the Jag a cooling system go over, flush refill, new hoses and expansion tank cap. I used the existing coolant type G-05, it is the original fill type and has worked just fine for 13 years.
I had 2 issues , the first was with the clamp at the radiator for the lower hose, some bright spark had installed the clamp with the tangs facing downwards. I cut it in half with a Dremel tool, I couldn't figure out how to get it off without removing the radiator. Second was the after market Australian made lower radiator hose. The Jaguar original is about 1/8 larger inside diameter at the radiator end than the after market hose. There was NFW this hose was going to fit the radiator with the restricted access. I went and got a Jaguar original lower hose and it went in easily , and it was only $10 more than the after market hose.
As I was replacing the expansion tank cap, I took the old cap, drilled a 1/2 inch hole thought it and used JB Weld to mount a short length of copper pipe through the cap. Screwed onto the expansion tank with a garden hose attached and the radiator drain open it was a way to flush the system. Worked pretty well, once it ran clear I ran it for an additional 10 mins. I finished off with a distilled water flush then 6 quarts of Zerex G-05.

 

Good on you, Gerry,
That's what I like about this site, I learn something every day I'm on here!!
I hope your XK8 keeps you happy, all those curves, nothing like it!
Stu