Want to fit power shower but poor hot water pressure

Hi Gaz A power shower has a built in pump and is fed by two pipes, one directly from the hot water cylinder and the other from the cold water storage tank. They look similar to electric showers and will indeed have an electrical supply, I think maybe you're talking about a thermostatic shower, these are the type of showers that you can fit a pump to, use a twin pump though and just like the power shower supply it with the same two feeds. Feeding it directly from the mains will most likely cause it to become unbalanced, follow fitting instructions carefully especially the hot connection, they will recommend using a surrey flange or similar to prevent the pump from drawing air. Good luck