I need to point out an error in the Warren Henry online parts catalog. The only place the DBC11380 bulb is used in the XK8 is in a couple of interior courtesy lights.
For the instruments, there are two different bulbs used; one for illumination, which Phil needs, and one for the warning lamps. And just to make matters more confusing, the current Jaguar Parts catalog has the part numbers for the two instrument bulbs backward. I long ago made a note in our catalog so we can keep them straight.
LJA4390BA = Illumination Bulb
LJA4390AA = Warning Lamp Bulb
Cheers,