After exhausting every possible cause of my door lock issue, ive decided to swap the BCM. Now, i believe its the coloured box at the bottom of the ICC? And i've been told that if i get the same coloured box from another car, it's a plug and play thing. Is this correct? Or will there be issues with the car starting etc by swapping BCM's?

NO it IS not. If you replace the BCM you WILL need to go to a Ford dealer to have it integrated into your system. You CAN replace the one you have with a High Series one which you can either buy NEW from Ford or get one from Ebay?

The Low series one is Blue while the High series one is Green. If you do buy a new one, there is also a black one which is very expensive but the green one will do the job.

Any mechanic with a reasonably up to date Carman, Snap-on solus or Modis and any number of other decent scan tools can perform the needed procedure.
It is a blatant LIE if any ford dealer tries to tell you that ford are the only people that can do this.