Thanks epapp , that's true too what you describe about the piston, but I was thinking of it being stuck IN , instead of out, thus pushing the pad slightly sidewards, and not letting it sit completely flat against the disc itself .
but , yes you DO have a very valid point there my friend.
Thanks to Gilles too for your advice . I have removed the wheel twice now , but it seems it will have to be a third time again LoLoL .
I will check about the spacers
Thanks Guys