What is involved in replacing shaver socket in the bathroom?

Jon, should be a straight fowward swap over, about a ten minute job to do. The new shaver point will need testing and a Minor Electrical Works Certificate with test results issued, as its within the bathroom and therefore covered by Part P of the building regulations. Some guys will argue that a certificate is not necessary as part p does not apply to like for like replacments, however any good electrician (NICEIC etc) should be issuing you with a certificate as proof that its earthed and safe etc.