Thanks for that. The only thing is it doesn't work! I get this message...
The new value for the button binding for the action Initiate Window Resize in plugin Resize Window conflicts with the action Window Menu of the General Options plugin.
Do you wish to disable Window Menu in the General Options plugin?
If I try any of the the 3 options that follow, apparently compiz accepts it, but nothing changes & when I go back to CompizConfig Settings Manager everything has gone back to the defaults.
Also, if I try changing the key from alt to ctrl, it modifies the settings for moving the window instead of resizing so there is something very buggy there. All those special effects, but something so basic doesn't work! I have now tried editing all of the settings related to moving, resizing & draging the windows - all I get is defaults or disabled despite the options which are supposedly there.