Hi,
The blend air door that is used to control heat is moved by an electric motor. Ive seen on US forums that these can gum up as the grease lubricating them hardens. They can be stripped apart and cleaned. They are also available new on rockauto.com if you need to actually replace it. Not sure if RHD and LHD use the same motor or a mirror image piece, but if you get yours off you can compare to the pics on rockauto. The link below is for the 4.0L but the HVAC motor should be the same for petrol and diesel models.
https://www.rockauto.com/en/catalog/jeep,1999,cherokee,4.0l+l6,1431776,heat+&+air+conditioning,heater+air+door+actuator,10721I'll see if I can find the repair thread.
All power for the windows goes through the drivers door switch. Most likely cause is probably a break in the wiring in the door jamb.
For locks check fuse 15 and circuit breaker 28 in the interior junction block. All power for locks routes through the passenger door lock module. Again possibly a break in the door jamb wiring.