Jaguar X300 battery has gone dead, and boot wont open. The key is not being accpeted. What can I do? Is there a way to open the boot - or can I charge the battery any other way?

there is a battery pos post under the bonnet/hood but you should be able to open the boot/trunk using the manual key access in the boot /trunk plinth unless its siezed cos it has not been used try a bit of wd40 and work the key gently till it gets free

So recharge the battery and open the trunk!

The key pad will not work but the phyiscal key should work in the key hole above the plate area.

the wiring around the trunk/boot hinge may be broken/opencircuit. the security system thnks the trunk/boot is open use the manual key to get in to the trunk and repair the wiring

Sounds like a total battery drain - something left on that you do not know of? Open the boot using manual over-ride (ignition key or cabin pull cord)

crank relay on the front pulley or ignition module under the coil ,it has to one or the other

can you not open the bonnet?

jumper lead point under bonnet

If the locks are working whilst you are driving then more and likely it is the actual door lock assy that is bad. the solenoid go bad and can cause erratic operation. But unfortunately they are only available with the whole door lock/latch assy.
I would disconnect the drivers and see if the problem still exists.
JPTCAT

the battery has gone dead you can not open the boot/trunk with the electrical system but you should be able to get to the battery by using the key in the lock on the outside of the the trunk its either in the xj badge or the number plate illumination holder. if you can open the engine compartment there is battery pos power points so you can jumpstart/power up the car