5 Answers

check it doesn't have a water saving device fitted, mine did and it was like showering under a fast drip, I asked a friend and he told me how to remove it ,relatively easy and 100% better

I would first remove the shower head and make sure it's not clogged up with lime/scale..

I am with Vinny and lambshank problem is with the shower head . You should have 35lbs at the curb ,this means out side faucets . Not practical in the house . With shower head off try turning on the water and check pressure . Hold the hose or life will get very interesting and messy fast . LOL!                        Bill

When I removed my shower head I found a plastic washer that reduces the volume of water  and mine was clogged with lime deposits too. That helped a lot. But when my water supplier decided to reduce the system-wide water pressure, I took the plastic washer out of the shower head. 

You can increase the pressure by reducing the size of your head shower. the smaller the more pressure you'll have. hope that help?