I've owned four Jags and a number of other cars, mostly bought on the basis of an emotional response rather than practicality. I can't say that the purchase of my 2000 XK8 was a purely rational choice, but a decision based on lust rarely is. With the intention of trying to head off many, if not all of the well-know problems, I used this marvelous forum for research, found a local indie Jag shop, and off we went. Here's what got done:

Primary and secondary tensioners (originals hadn't cracked yet)
Water pump
Thermostat housing
Upper, lower and bypass radiator hoses
Serpentine belt
Spark plugs
Air filter
Oil and oil filter
Had them install an updated Sunbelt transmission valve body that I purchased directly.
On my own, capped off the hydraulic lines to the top latch

Yes, it cost some $$$, but not nearly as many as having to replace an engine or transmission. Hopefully I can enjoy driving with the hopeful expectation of only having to deal with some relatively minor repairs and maintenance over the next few years.

Can anyone tell me if I missed anything of importance?

The other significant experience on these cars is the front suspension bits. When tire wear becomes a problem then it is probably time to do the full Monty.

Thanks, I thought about that also. Checked the measurement between the center point of the front wheel and the lip of the fender which came in at 15", so I figured the shock mounts were probably okay. The alignment was okay when checked during State inspection, so I'm hoping to get a year or so out of the front end before it becomes an issue.