The water pressure from my shower is low, we've been using it for several years but it's only in the last couple of weeks that we've had the problem. I've cleaned the showers head and hose, don't know what else I can do before getting a plumber. We've had the shower nearly nine years but didn't want to buy a new one and have the same problem. It is an electric shower if you hadn't already guessed.
Does the pressure return to normal if you reduce the output water temperature? Some electric showers will regulate the amount of water flowing through them to allow the water to reach the set temperature; at higher set temperatures, the flow rate is reduced so that the water remains in the heater longer. Given that your symptoms appeared recently, it could be that a heating element failed.