I need to remove my passenger seat, and disconnect air bag etc so I can 'properly' fit my DVD changer etc etc
Does anyone know if the electronics / airbag warning system will get upset......

Would rather not take it to a dealer post ICE mod to get airbags reset etc 

try emailing sponsor 10forcash for the cost of an airbag reset, explaining what your doing, if it does need reseting he should be able to do it with his computer system for you, but cost will depend on location  Former Mod/Member, with the most post & Chicken George Arch nemesis

Disconnect a battery during all time of your operation and everything wiil be all right 
Freelander II 2,2 TD SE Stornoway Grey

Sorry for my wry English. I began to study it recently.
I'll be thankful for your corrections of my mistakes

AS LAR has stated disconnect the battery first as all systems are monitored and if some thing is disconected it will trigger a fault code on the ecu which will then have to be reset for the component to work.
Should you have any problems landrover shouldnt charge you to much to reflash the ecu or if its still in waranty just tell them a light has come on and denie removing anything

But after disconnecting the battery, wait a while, at least 3 minutes, because SRS system uses energy reserve capacitors to keep the system active in the event of electrical supply failure under crash conditions.
It is necessary to allow the capacitors sufficient time to discharge (3 minutes) in order to avoid the risk of accidental deployment.