Just done it.....
Remove hatch at bottom, rear of the machine. On the right as you look at is is the pump and a 3-way black rubber hose. Loosen the large jubillee clip securing the hose to the drum, then the plastic clip securing the hose to the pump. Warning, this clip will need a pair of water-pump plers or similar to do it up tightly again. The hose can then be pulled out of the hatch, enabling you to loosen the jubilee clip holding the hose to the water level sensor tube. The filter resides inside the hose....if it's anything like mine, it is encrusted in gunk, scale, pipe-cleaners!!, 5p coins and nefarious pieces of plastic. Don't forget to clean the fixed orifices on the machine.
Replacement is the reverse of removal.
This is one of those things not covered by warranty, yet they make it very difficult to do and exclude reference to it from the user manual. Most kind.
Richard
January 2010