thanks will take a look at this but it does sounds outside my wheelhouseIt might have jammed because they work on a type of ratchet that hooks on when closed then a spring takes the tension off and latch is released when you press down again ( difficult to put into words). Just undo the plastic waste pipe and there will be a large nut holding the rest into the basin which you unscew and then lift out the waste. If you have no access then you may need a plumber.
