Electrical work in the bathroom should rarely be attempted by DIYers - you may be breaking building regulations if you do it yourself.
Play safe and employ a qualified and reputable electrician, who will be able to make sure that the work’s safe and legal.
If you’re buying electrical fittings (in most cases, lights) for the bathroom, make sure that they’re suitable for the ‘zone’ they’ll be in.
The zones are worked out according to their proximity to the taps, shower and bath, etc, and all good retailers should say which zone or zones bathroom lights are suitable for. Some even have a diagram of the zones on the box, although you can easily find this online.
The only electrical sockets allowed in bathrooms are razor ones and the only switches should be ones operated by a cord pull, or special ones for, for example, an extractor fan.
Alternatively, you can have a normal light switch on the wall just outside the door, although this isn’t ideal if you want to put the light on when you’re naked and already in the bathroom!
If you don’t have an extractor fan, get an electrician to fit one. Extractors reduce the damage caused by steam and condensation and help to prevent mould and mildew from forming.
In bathrooms without a window, which is common in flats, an extractor is even more vital and should be switched on every time you take a shower or bath. Many extractors are wired to come on when the light does, although they can be switched off independently.
If you’re making changes to the water supply, it’s a good idea to check with your water supplier that you’re not breaking the bylaws - your plumber should be able to advise you.
And if you want to find out if building regulations apply to the work, try www.planningportal.gov.uk or your local building control department.