I swapped the pollen filter in my Picasso yesterday. A very easy job via the access slot in the engine bay. One just needs to wear gloves and arm protection to avoid scratches from the sharp bits on the slot.
Good tip about Dettol Paul
I can not remember where I got it from but once paid a dealer to disinfect the air con and the smell after was identical to the Dettol stuff and not perfumed. Another time I used an aerosol that was set off in the car with it on recirculation and smelt of apples. For cars with the pollen filter under the scuttle, with the filter removed and the cabin blower on high to the central vents, I use the garden sprayer on a fine mist to spray it in where the filter was, turn off the blower and let it dry on the evaporator. It will drip out of the heater drain and help keep that clear. I use Dettol Antibacterial Multi Surface Cleaning Spray 750ml poured into the garden sprayer.