Hi everyone, thanks for your replies. I think it would be best just to leave and like you say if I needed to access it for any reason I can get to it by some means, either smashing or via neighbours. There are no smells from it either and all the sinks etc run freely.
Hi, Just after some advice really.
In my conservatory the tiled floor has an area that has a strange pattern (see photo). Upon investigation (Google etc) I now know that this is the inspection cover to the foul drain or sewer. So looks like the conservatory was built over the drain some time...