New owner with various faults, help needed please!

New to the forum, i got my first range rover last week, 2003 TD6 HSE and have had a few issues with it so far. The pixels on the dash was unreadable so i ordered the new ribbon and fitted it today. Pixels are now working again but when i have put all the dash back together and took the car out for a drive to the shop, i noticed the speedometer seems to have given up. Its not moving at all. I did flatten the battery by accident whilst i was inside doing the work, left the sidelights on. When i got back in the car after leaving the shop i noticed the "HDC fault" thrown up on the dash but quickly disappeared after starting the car. Had a fault with the air suspension since i got it, had it plugged into the computer and it came up with "reservoir pressure static when filling"... mechanic cleared the faults and suspension worked for an hour or so before locking back into normal ride height. The other thing that is peeing me off is when i lock and unlock the car the hazards dont flash... could all this relate to a knackered battery? Any help with any of the issues will be much appreciated

Hi, you might want to post this in the range rover section you will get more help there, first thing with any range rover is start any fault finding with a very good known battery as they will throw up all sorts of weard stuff Just for the he'll of it.
if you get a new battery get the biggest ah one you can fit in iirc 120 ah 1000cca is good.