Thanks Kyle, dead easy, just the one Torx screw you can see in one of the pictures on the side, then the whole unit slides upwards to release two plastic "claws" that locate the unit into the metal underneath on the floor and that's it. No other parts to take apart, literally took just a few minutes.
Only thing I did to do was slightly trim some plastic from the claws in the new parts as they were a bit tight compared to the original and I didn't want to snap them off when thumping the new unit down into position with my fist, and worked like a treat.