Gas BBQ & gas bottle (Leslie KY6)

We inherited this Argos 3 Burner Gas BBQ with side burner, so don't know if it works. There are patches of rust and it needs a really good clean. We do have the Assembly User Instruction manual. One gas bottle which appears full. To go together. (Be aware that the gas bottle when empty must be returned to the supplier, ie exchanged for a full cylinder.)