I have just fitted a Grundfos Nile 1.5bar Shower Pump to a hot water cylinder / cold water tank gravity system. I fitted the pump next to the hot water cylinder at the source of the hot water, however there has been no increase in the flow of water to the shower. The pipes are all clear and the filters are also all okay. I am at a loss as to why this hasn't solved the problem, have I fitted it in the wrong place? Or is there any other reason why it has failed to make a difference? Any suggestions are appreciated.

You are apparently not USA. Most of the people who participate here are USA Your are describing a system that we are not familiar with. You need to describe your plumbing system more completely.
With all that being said, check the installation of the pump and insure that you have the flow in the correct direction.