Yes, desperate of Emsworth, we have the same problem. The small amount of water loss adds up if you have a metered supply to a hefty 'half as much again' on our water bills incoming and waste!
It would be cheaper to rip it out and go again, I estimate. Replace the whole unit or change to a traditional flush, if you can. Some plumbers will not fit this new press-button flush - I wonder why?
Martyn of Bexhill
November 2010