The rubber over flow tube from just below the pressure cap on the header tank.

The tube disappears into the fender behind the brake master cylinder.

I blew into the tube to make sure it was clear and i heard bubbling from back towards the trunk area.

I put a Mity-Vac suction pump on the tube and pulled a vacuum, and I got a bit of antifreeze in the tube, then more gurgling (sounding from) back by the trunk as it started sucking air.

I wasn't aware of any other coolant catch can in the system.

Thanks,
Doug

 

It goes to the atmospheric recovery bottle. If you just look at the Jaguar parts website, you can see all the components.

Paul

 

It goes to the atmospheric overflow tank in the wing cavity behind the wheel baffle:
https://parts.jaguarlandroverclassic.../brand/jaguar/

The hose you blew into is no 7 in the above diagram and it should be joined to the pressure tank overflow spout shown in thjis diagram:
https://parts.jaguarlandroverclassic.../brand/jaguar/
The same hose is part number 5 in this second diagram.
The fact that you heard bubbling is good as it means the line to the overflow tank is connected. In principle the idea is that the header tank is always full and coolant expansion flows in and out of the atmospheric overflow tank.