May be a daft question but Why do you have to remove battery earth when charging via a battery charger? What if you use a trickle charger, is that the same? I've just fitted clips and gone ahead.! 2009 Range Rover Vogue 3.6TDV8, Bournville, Parchment/Navy
2005 Jaguar XJ350 3.0 V6 Sovereign, Jaguar Racing Green, Ivory
1997 TVR Chimaera 450, Formula Red, Grey

^^ On this occasion it was to ensure the battery could be charged without the possibility of the charge simultaneously draining down through a faulty alternator to earth. Assuming of course the alternator is faulty.
At least this would guarantee the battery could be charged.
Normally just charge the battery with the earth connected, no problem.

BFB, without seeing the car all we can offer is conjecture, however to have a sudden total electrical failure like that does not in any way sound like the battery. And even if the alternator failed the car would continue to perform normally (save for the battery warning light on the dash) until such times as the battery ran out of charge.
No, something has failed suddenly and my guess, and this is only a guess, is the engine to chassis earth strap has failed. These can and do fatigue over time and it’s possible it’s now snapped. This is one of the few things that would give you the symptoms you describe. If it is this, and it’s a big if, then it’s a fairly straightforward repair.
Anyway, there’s my thoughts, hope you get it fixed without too much bother.

Thanks nicedayforit! Now understand and put my mind at rest. 2009 Range Rover Vogue 3.6TDV8, Bournville, Parchment/Navy
2005 Jaguar XJ350 3.0 V6 Sovereign, Jaguar Racing Green, Ivory
1997 TVR Chimaera 450, Formula Red, Grey

@ Sam.
I agree with what you say regarding the battery not being at fault. The notion of a failed earth strap had also crossed my mind but the issue is clouded somewhat by the fact that 2007 cars seem to suffer an unusually high rate of alternator failure for some reason. It is really a case of logically dealing with each possible cause of failure in turn.
Regarding failed earth straps, having come across a number of these in dubious condition over the years - not helped by manufacturers installing them in most unfortunate locations, I always as a matter of course with our cars fit supplementary earth straps in more suitable locations.

Just to update what happened with this saga.

AA came out to look at it on the 4th January and got it to start with his booster pack. But as soon as he disconnected his pack the car shutdown. He tried twice more just to be sure, and the same thing happened both times.

So the car was recovered to my mates garage where he was happy to have a looksee for me.

Picked the car up tonight with its new alternator fitted, and a new fan belt (my mech said it’s what he always does, so who am I to argue) and the car runs like a dream.

Turns out the bearings in the old alternator where pretty much shot, hence the whining/whirring noise I first noticed a couple of weeks before it finally gave up the ghost.

He also said there were many many faults showing when he plugged the computer in, most of which he thought related to the failing alternator and battery. He cleared them all down and checked any he was dubious about, but it seems I am a lucky little bunny and bought well 4 years ago when I chose this car.

Thanks to fellow members for all the ideas and/or advice when I first posted about the cars problems, much appreciated.