A single pole will not disconnect all live conductors as per the regs quoted Section 721 in the regs is a special section just for campers as they are classed as a high risk The regs for a buildings only requires a single pole.
As this is dealing with Mains 230v The regs require you to be competent person this would normally be a qualified electrician who has carried out a apprenticeships as well as a qualification in the latest regulations (17th edition of the iee regs) A auto electrician would be unlikely to have these
