I have a concealed cistern with plastic fitting through the sid. From the plastic, there is a steel flexi pipe across the top of the Dudley dual flush, with a half turn valve and loose running nut connecting to the float valve assembly. The half turn ball valve is leaking (throught the centre not the fittings threads) at the opposite side from the actuating slot. If left fully open, it sprays out, so I assume the valve seal/seat is knackered. The cistern fills and the overflow back to the toilet bowl is continuously running. Is the flexi/ valve, a standard off the shelf part. Cheers.