Help please. E38 750iL won't start.

Hello E38 Fans.
Well, I bought an E38 750iL and got it home Friday night (travelled about 200 miles from dealer). Drove yesterday also, maybe 20 miles. Both days so far it has been fine with no indication of any issues.
Tonight, I go out to the car, unlock it using the remote, internal lights all come on, etc...still no sign of any issues. Put the key in the ignition, turn it to start....nothing, except 'Ping'...check number plate light....check fog lights...transmission emergency mode...monitor flashes and goes crazy...lots of noise from the dash...but not a sign of life from the ignition. Take key out. Put it back in and try again... 'Ping'...check headlights...monitor flashes and goes crazy...lots of noise from behind dash...but again...nada. All internal lights, headlights,etc working no problem. If I try to start with headlights on they also flash and go crazy, just like the nav/tv monitor.
Help please. Every time I try to start it, it throws up different error message each time...none of which are true (like check headlights when I switch them on they are all fine).
Any ideas? Have I just thrown good money down the toilet? :-(

Check the battery voltage--if it is under 12.5 volts it needs to be charged and load checked-AutoZone and other parts stores do it for free.

If it is OK then the alternator output needs to be checked.

Terry, thanks for your quick reply. I hope it is only the battery. ;-) I'll let you know.

OK, I checked the battery today... 8.5v according to the OBC test #9... so no surprise it won't crank.
I've put it on charge and will then check if it can keep its charge. Anyone know how I can check if the problem is battery only or if there's a problem with the alternator instead? Or is a battery health check the only option?

Slight problem with the battery if I need to change it. It is the old-style single by the way and someone has tightened the bolts onto the + and - terminals so hard that the bolts are bent. I can't undo them... looks like I may shear them if I give any more torque. Anyone had similar bolt issue and managed to get the damn things off?

Yea, I know lots of questions.;-)