OK - take out two crosshead screws on the hinge side. open it up a couple of centimetres. insert a knife blade on the opposite side (at end away from controls) up into the top section to pull it away - it comes quite easily and does not damage the plastic. reinsert the knife at the control end to pull the top outwards (needs a little more force) and then the whole thing comes open. it just clicks back together again and reinsert the screws.
chris marlow, October 2011