Problems with Grundfos UPA 15-90 Booster Pump

I have been suffering from very low pressure and flow rates on my hot water system (vented) and hoped to solve the problem with the Grundfos booster pump as there is no possibility of raisng the level of the header tank. Because it seemed that the problem revolved around the head of water entering the cylinder I fitted the booster pump to the supply to the cylinder from the header tank.
When I tested the installation after fitting the pump, the pump switched itself on automatically when a tap was opened but would not switch off when the tap was closed. Hot water in the cylinder ended up beiing pumped up through the vent and back into the header tank. The only way to stop this was to switch the pump off.
What do you advise?
Have I fitted the pump to the wrong side of the cylinder? Should it be on the hot water supply side?

I would appreciate any advice/assistance anyone can can give.

as you have found out if you put it on the supply side it just pumps up through the vent, you need to put it on the hot water outlet side of the cylinder.

Thanks!