The following information is a guide to help you understand what fittings can be placed where in a bathroom. This is not an installation guide and reference should be made to the IEE Wiring Regulations (17th Edition), if you are in any doubt contact a qualified electrician.
Firstly it is important to understand the rating by which bathroom lights are classified. IP rating stands for "Ingress Protection" and is always followed by two characters. These two numbers refer to the level of protection and it is important that you choose fittings with the correct rating according to where they are to be sited within the bathroom. The diagram shows a bathroom split into four zones: 0, 1, 2 and 3.
Zone 0, the area inside the bath or shower itself. Any fitting used in this zone must be low voltage, (max 12v) and be rated at least IP67 which is total immersion proof.
Zone 1 is the area above the bath to a height of 2.25m from the floor. In this zone a minimum rating of IP44 is required. If the fitting is 240v a 30ma residual current device (RCD) must also be used to protect the circuit in this zone.
Zone 2 is an area stretching 0.6m outside the perimeter of the bath and to a height of 2.25 from the floor. In this zone IP rating of at least IP44 is required. In addition it is good practice to consider the area around a wash basin, within a 60cm radius of any tap to be considered as zone 2.
Zone 3 is anywhere outside zones 0, 1 and 2 (subject to specific limits) and where no water jet is likely to be used no IP rating is required.
In addition to the above, if there is a likelihood of water jets being used for cleaning purpose in zones 1, 2 and 3 a fitting rated a minimum IP65 must be used. Full details can be found in the latest copy of the IEE wiring regulations.