EUREKA!
Prise off top and bottom trim cover on the left hand control plate - they slide out forwards - and you will see the cover screws.
SneakyPete, December 2008
I have just read your question again, when you say "Top screws" I'm confused, there is normally only one screw at the top and one screw at the bottom behind the bottom cover. I assume you have removed this one.
Colin, November 2008
There shouldn't be anything holding it once you have removed the two screws. It may just be a very tight fit. Try getting a thin screwdriver in where the cover meets the unit and twist and pull the cover at the same time, be careful not to damage the plastic.
