Help fixing leak when flushed?

I have a Villeroy omnia toilet that is attached to an enclosure. The enclosure houses the cistern. I am experiencing leaks from under the toilet where it attaches to the 'wall / enclosure' only when it flushes. It is not waste, but water leaks when the cistern is refilling the pan from underneath the toilet.

I have had 2 plumbers look at this now and still no joy. I have had the pipe connecting the pan to the waste pipe replaced to a flexi connector, and the seal around the inlet pipe from the cistern to the pan replaced but i still experience the same problem.

someone help!!!!

GAV
February 2009