Yeah i put the black seals back properly, but it looks like the plastic pipe was cut at an angle. I forgot to mention that i have already put a bottle of Mr Muscle sink blockage formula down the sink, but it did nothing.
I live in a flat, and about two weeks ago noticed that the sink was draining water away very slowly. I haven't got a plunger, so i took the pipe apart from under the sink and cleaned it out (there wasn't much crap in there to be honest). I also unscrewed the pipe it was attatched to and cleaned...