The water continually runs after flushing the toilet, the only way to stop it is by pushing the flush button continuously until it stops. I have looked inside the cistern but really don't know what I can do, the toilet was fitted under a year ago from new ?

Sounds like all you need is a flapper adjustment.
With the flapper seated the linkage wants to have 1/4" of play. Too much play and the flapper doesn't get pulled back enough giving you a short flush. Too tight and it lets water seep past the flapper. I adjust the chain by the link and if it needs fine tuning, I bend the flush lever rod a bit until I have the desired play in the linkage. One more thing about a flapper. you will see where the old flapper hooks onto the base of the white overflow tube. On a older type with no hooks the flapper has a ring that slips down over the overflow tube to the seat,(see image). If your tank has hooks, take a sharp knife or scissors and cut the neoprene ring off on the marks provided and hook the flapper on the hooks. Leaving the ring on will interfere with the flush. The water level in your tank should be 3/8 to 1/2" below the top of the overflow tube when the tank's filled. And the little tube wants to run from the ballcock and connect to the white overflow tube.. Good luck, Tom

If pushing the flush button several times stops the issue it may just be that this button and linkage needs a lub job. It sounds to be that it is hanging up and not allowing the flapper to drop all the way down. Look inside the tank, there are not may places of movement with a button, spray WD40 inside the buttom mechanism from inside the tank and wiggle the heck out of it, any better?