The property is about 25 years old and has the original wiring, with RCDs on each circuit. Sounds like you are suggesting that I should cross bond it but there is no easy connection to the shower hose/valve and I dont really want the cable appearing in the shower. It changes to poly pipe as soon as it goes into the wall so there is nothing to fix an earth strap to.
There is an extraneous-conductive-part and an exposed-conductive-part today treated very different. Door handle could be an exposed-conductive-part where as extraneous-conductive-part means in layman's terms something which could transmit a fault from one area to another. So don't think you really need to earth metal pipes which have one foot or more plastic feeding them. This is what the regulation says:- 701.415.2 Supplementary equipotential bonding Local supplementary equipotential bonding according to Regulation 415.2 shall be established connecting together the terminals of the protective conductor of each circuit supplying
Class I and Class II equipment to the accessible extraneous-conductive-Parts, within a room containing a bath or shower, including the following: (i) metallic pipes supplying services and metallic waste pipes (e.g. water. gas) (ii) metallic central heating pipes and air conditioning systems (iii) accessible metallic structural parts of the building (metallic door architraves. window frames and similar parts are not considered to be extraneous-conductive-parts unless they are connected to metallic structural parts of the building). Supplementary equipotential bonding may be installed outside or inside rooms containing a bath or shower, preferably close to the point of entry of extraneous-conductive-parts into such rooms. Where the location containing a bath or shower is in a building with a protective equipotential bonding system in accordance with Regulation 418.104.22.168, supplementary equipotential bonding may be omitted where all of the following conditions are met: (i) All final circuits of the location comply with the requirements for automatic disconnection according to Regulation 411.3.2 (ii) All final circuits of the location have additional protection by means of an RCD in accordance with Regulation 701.411.3.3 (iii) All extraneous-conductive-parts of the location are effectively connected to the protective equipotential bonding according to Regulation 422.214.171.124. NOTE: The effectiveness of the connection of extraneous-conductive-parts in the location to the main earthing terminal may be assessed. where necessary. by the application of Regulation 415.2.2.
Google Earth Clamp EC16 Pack of 5 and you will see how to connect but I don't really think it is needed. However I don't have a 25 year old copy of the regulations to look it up.