Thanks to all the posters its been a lot of help.
Changed mine on my "new" 2008 V50 today. Took me about 2 hours including rain and tea breaks. Looks like it either hadn't been done ever or at least not very recent. The change in the amount of airflow coming through the vents is dramatic.
When (if) i do it again, this is how i did it.
Disconnect the battery as precaution but as not unplugging CEM up to you.
Remove panel behind waterfall console.
Remove glove box (labelling the wires)
Remove inner glovebox
Lower the CEM, get it off of its bracket and pull the carpet down
Move the CEM out of the way as far as possible
Use a angled ratchet spanner and a hand finger ratchet with 13mm socket to remove the CEM bracket bolts
Replace pollen filter hoovering out its recess and the carpet.
Put back together
Go find Savalon and treat all cuts and scrapes
Whilst i had the glovebox out i cleaned the air temp sensor and changed the glovebox & footwell lights for LED so a bit of a bonus.