Ive just bought 3 filters, I know where 2 go, but where does the Pollen filter go?

Usually in a slot above the passenger footwell. (Citroen Xantia anyway). With a torch to illuminate the underside of the glove box area, lie on your back. You may see a plastic slide with an arrow pointing left (or right). Carefully prise it apart, it's easy to break a lug off. Pollen filter inside. Will be covered in bits of moth, dust, leaves. Replace with new one, put that one in the washing machine net for delicates and save it for future use. DaveK.

early ones don't