sorry knobby but yes it would
due to the way they work ie bigger element so you can let the water flow through the shower at a faster rate to get the same heat
As per the last 2 answers.. However the pressure as experienced at the nozzle can never be greater than what you currently get with the temperature setting control turned right down.
8.5 should be adequate for an electric shower, if your water pressure is low, upgrading will not improve the flow, first thing to do is check that stopcock is open enough then clean out the shower head, and if you do upgrade as zig zag says you will need to make sure cable is big enough.