Hi people. Just moved and downstairs shower is draining slowly. Almost certainly blocked by previous residents. My first reaction is to manually clear hair etc from the top, but I can't get the grid off. It's a plasticy thing with chrome coming off. Ideally I'd replace the whole trap but it's a downstairs shower with no access at all under the tray. Photo shows the plughole. How can I shift it without breaking it, and can I just replace the inner grid?