if your button is like mine, round one with a cresent shaped one around it, push the round one down,then pull the cresent shape one up, i had to lever a screwdriver under it,, then take out round one, you will see a screw to unscrew then you can take your lid off,
just found that out on this site,, hope this helps
welshguywxm
January 2011
Depends on type if Roca push down short flush round button and hold it down with small thin screwdriver gently prise up the full flush halfmoon plunger/button and it will come out take out the round one and there should be a plastic bolt/screw holding the lid on unscrew job done.
Bob
January 2011
Unscrew the chrome outer ring around the buttons,it will only be finger tight.Good luck.