I have two of them, which I have pulled apart to clean and service. Mine however are slightly different and do not have circlips. They had a curved nut at the top, which allows removal of the handle. Then you need to unscrew the "core" from the lower part of the body with a spanner. This bit is quite hard to do if you haven't done it before, it can be quite tight and not particularly obvious. Make sure you note how the whole thing is put together as there are A LOT of parts to these things and there are more than one way to reassemble them (not all of which work).