Great care needs to be taken when choosing bathroom lighting as the regulations are strict concerning the type of light you can use, this information is not an installation guide and reference should be made to the IEE Wirings Regulations or a qualified electrician.
Inside the bath or enclosed shower cubicle, fittings must be low voltage (12v max) and be rated at least IP67. Above the shower head in an open cubicle fittings must be low voltage (12v max) and rated at least IP65.
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.
The area stretching 0.6m outside the perimeter of the bath and to a height of 2.25m from the floor. In this zone a minimum rating of IP44 is required. In addition it is good practice to consider the area around a wash basin, within 60cm radius of any tap to be considered zone 2.
Anywhere outside zones 0, 1 and 2 (subject to specified limits) and where no water jet is likely to be used. No IP rating is required.
In addition, if there is a likelihood of water jets being used for cleaning purpose in any zones a fitting rated a minimum of IP65 must be used.