Dripping toilet.... arghh!!!!

[MasterAbacus]

Hi all, for about two weeks now our toilet has been dripping.... I asumed it was the over flow dripping back into its self....

Anyway, after an evening of nagging, ive just been and had a look.... Its not the overflow.... the water level is a good inch below that pipe....

Anyways, im 99% certain it dripping into the pan from the cystern, but where from ive no idea? Im thinking the flushing mech... its one of them single push down jobbies....

I could prob sus it out, but thaught it might be quicker to ask here and maybe get a direct pointer... to save me some time...

Any advice as always greatly recieved.

 

[hi-spec plumbing heating]

hold the mech about half way down and turn it. it will come apart check the rubber washer at the bottom of the valve and clean.
sometimes they can go out of shape try turning it around.