no a normal size wheel will not fit in the hole.
looked at swaping our bicycle trye for the spare on our mondy cos that had a foam spacer round the wheel well to bring the boot floor up to the level of the wheel,can be done but the bolt that holds the wheel in the well was differant thread from mondy so could not use the longer bolt in c-max
that was with the standard 16" mondeo wheel, for some strange reason it had a full size steel spare(loosing 50 ltres of boot space in process), was wanting to use it cos max looks realy pants with the space saver on with 17"wheels
ravenger is right the wheel is approx 40mm widerfor a standard wheel over the space saver, so to make the boot floor flat they have to move the floor up with a false one. on our mondy that was done with foam, raising the floor means that you loose some boot space(25-35ltrs) on a max.