Thanks MVacs. I did groan to myself when I started looking at all the picture instructions, but cheered up when I found some actual words underneath!
I have rinsed out the top filter and removed the one in the ball. This second one looks like it's made of paper - does it really need rinsing out under a tap? Won't it disintegrate?
(Edit to add: it's a DC50 ErP if this makes a difference)