Pmetcalfe, in post #11 you stated that you would investigate whether the circuit was RCD covered and now you plan on RCD Fcu feeding the socket. You need to be careful on here that you tell it as it is. When there's blood in the water they can smell it!
If this is your dwelling, tell it as it is, be honest and the forum is willing to help. Read the books, take a look at appendix 15 in the BS7671 and acquaint yourself with fault protection requirements and additional protection. You'll need to do a lot of archive reading from the forum - use the search button and get immersed, that's were you will get your answers. All respect intended. Rob