Thanks for your help. Our boats must be identical twins! Same layout and age. Found the battery thanks.
In the service battery department there are two unconnected cables, one red, one black. Have tried to trace them but no luck so far. I wonder whether they allow the starter battery to be be connected to the service batteries or allow the starter to be connected to the service batteries in the event of the starter battery failing? Do you have the same cables? There are about 5-6mm dis so are power cables -I think.