Thanks for the input everyone,
Planning on getting the battery replaced because I realise it might have just reached the end of its life.
The question on the seatbelt warning system was due to a fear this might be draining the battery and if not fixed will just drain the new battery once installed.
Up until recently, if the driver or front passenger didn't use the seatbelt there was a warning light on the dash and a sound but after a recent holiday where the car was fully loaded one of the back seat passengers had dislodged a module from underneath the driver's seat and since then no sound is emitted when either the driver or passenger don't use the seatbelt although the module which has 2 connectors seem to still be connected.
This was a few weeks ago and up until Monday of this week there were no battery issues when the dashboard displayed a warning to recharge the batter by driving and the car does a mix of short and long trips (on Sunday the car had done a 2hr round trip so would have expected the battery to be topped up and charged from this trip)
Thanks for sharing the link for the manuals; I'm living in EU and the manual supplied with the car isn't in English so will read the English owners manual later