Noticed earlier on today, on turning the HGT off at the works car park, the battery symbol appeared on the dash - normally this wouldnt spook me out, but it was after killing all power from the car (and removing the keys from the ignition)

Not sure if this was just a blip, or possibly a sign the alternator or battery are on their way out?

Also, is alternator replacement another engine off the mounts job? Or can it be done 'in situ' with relevant access to the engine?

Thanks for any help!
Martyn