I wish . . .
"Fixed-head" means coupe, or "not a convertible." It could also mean that if you own one, your head needs fixing. I have heard Jaguar described as "The car you will curse every day you own it, and still stand in line to buy a new one." I think that's a little harsh. My Jags were -- in memory's kind light -- no more unreliable than other British cars of the period. "Damning with faint praise" that may be.
I have heard that the MG T-series and the XK120 were responsible for exciting post-WWII America about sports cars. Certainly they excite me! XK120's have an early version of Jag's DOHC inline 6, with a four-speed non-synchro-first-gear gearbox that -- to shift smoothly -- asks both force and finesse. I love the XK120's slinky 1930's/1940's styling; the coupe body is not unlike the Bugatti Atalante. (Not that I have ever seen one.)