Not if you are replacing an existing shower with one of the same kW rating. However, you do need to be competent to do it, and your use of the term "power point" worries me slightly. I assume you are referring to a isolating pull switch.
The problem comes if you want to fit a larger rated shower which needs larger cable and MCB. Then it is not a like for like installation and if you want to DIY, you need to inform your local council building control before you start. They will inspect the installation.
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