Just fitting a battery will not magically cure the SRS fault.....BUT, it will help in preventing further issues.
The Range Rover is a very power hungry beast, and they consume huge amounts of power just to keep the dozens of ECUs fed and operating correctly.
84% is not a healthy battery to an L322, it may be for 'lesser' vehicles but as the L322 is so massively dependant on electrical devices, ECUs and the various databuses shuttling information backwards and forwards anything less than perfection can cause hiccups.
Just to shuttle the huge amounts of data around the the car for the various systems it uses 5 databuses - the I bus, K bus, M bus, P bus and the CANbus. then you have the ISO bus for the engine and gearbox dedicated diagnositcs.....
A good, strong and perfect battery is a must, but the low voltage and the couple of jumps you have had to have recently has already caused the SRS fault, a new battery won't miraculously clear the fault...you need to find out why the low voltage cause the ECU to fault in the first place....diagnostics will help you with this....you say you had it done, got it reset and the light then came back on again...had the fault read and it said something about low voltage but the technician didn't know why or what that meant - then you need to take it to someone who can diagnose and understand what the fault is telling them. Everything else is just chasing a tail.
Landyzone is a unique forum with a lot of micky taking and friendly banter, but the help and response times are second to none...so yes we may make a jibe and take the pi$$ but that is par for the course here, but you will also encounter some of the most knowledgeable and helpful people on here too.
Owning a Range Rover is the most rewarding and equally most frustrating endeavour - they will empty a healthy bank balance rapidly when they go into a fault, but when they are working they are the best thing to own and drive.....