Owning your own home

Can anyone give me a pointer on putting a new shower in my bathroom? I understand the practical differences between electric and power showers, but have no idea as to a rough cost difference. I've just moved in and cold water pressure in the house both upstairs and downstairs isn't great.

Currently there is just a shower head connected to the taps and the pressure is pitiful as the hot water tank is on the same floor as the bathroom. Decisions is:

• Get a power shower which has a pump built in to work with the pressure, but expensive.
  
• Get an electric shower installed (with a pump) which just works off the cold water but pressure won't be great.
  
  

Any comments/ideas on price would be really helpful.