leaking auto gear box on my mk 1 renault clio rt auto M plate 1.4?

please can any one tell me is it common for most clio cars rt auto boxes to leak from transmission sump, i cant see where else its leaking and i have resealed it once with silicone it only leaks on an off and only when its stood?
Also if not shore can someone tell me where i can take it to be looked at in sheffield who's good with autos an can put this wright an at a fare price, thanks.