Hi Dave,
Thanks for your reply.
The car was only doing short drives over the last year, but I am in Australia and we are moving around now so it has had some long drives. The error message seems to have cleared now and hasn't come back.
Only problem now is the comfort features don't work, such as welcome lights off, keyless opening etc. I read that when a battery is dying these features default to go off to save power, but now they won't come back on!
Cheers
Cameron