hey just did mine, different way though.
entry is via the small pull out section near bonnet release.
on the right hand side, under the steering wheel is a black box with 'smart entry' on it, size is about 4cm by 7cm
undo 2 screws to take the box off the holding bracket.
take out white plastic plug from box. (sticks in there pretty good)
the black surround around where the plug went comes out, you will see where u can put in a screwdriver to jimmy it out.
take out the circuit board.
match up where the actual beeper is from where the audio holes are on the side (it is a round black cylinder abour 5c piece in diamater and 10 cm high)
CAREFULLY either:
1- prize it off with a flathead screwdriver and pull out the terminals with some needle nose pliers gently (i did it this way easily)
2- get a solder iron and reheat/undo the conection from the back
put everything back the way you found it
this way it wont phuk with you alarm or windows or anything else, cos everything is as it was, just no noise cos obviously no beeper
btw car was a r33gtst S2, should take about 20 mins max, have fun