I've got an autohomes komet - 1986. The interior looks standard but the electrical wiring doesn't seem to be. For a pic of the interior have a look in the "garage". Sorry I can't work out how to put a link in

There is no leisure battery, no zig unit, no split charger or wiring to suggest there ever was any of these items. 12volt lighting seems to be connected to the main battery - and only works ocaisionally.
I thought it was time to rectify all this but I'm not sure what to do. I've been quoted a huge sum to fix the wiring (£500 - ouch!). Can any of you give me your opinion please?
I need to resite the battery (as I can't get one to fit due to the swively seat problem). There is a battery tray way back in the locker to the right of the fridge. I've been told the battery should go in a box not just in a tray is that right?
I think the locker to the right of the fridge is usually where the gas bottle goes. I've been told that the gas bottle can't be sited next to the battery or any other electrical stuff. Is that correct?
If so I'll have to resite the gas bottle. I was thinking to put it in the cupboard to the left of the fridge (below the hob and grill). Has anyone else done that?
Finally - I've been told that I don't need a zig unit, just a split charger. Will that do the job OK? or should I try and get hold of a zig unit?
Any help you can offer would be great. Thanks.