Stupid question? Do all mk 2 come / need a rear sway bar? I have had my escort for 15 years and never had one

Rod

Nope - not even most had them.
In Aus, only the Rally Pack and RS Mk2 models had them, and I have seen 11 and 14mm versions.  The mounts for them are on all Aussie Mk2 diffs and in the body too.  The LHS body mount is used for the exhaust hanger mount tack welded on if it was not factory equipped with the rear sway bar.
 
Opinion seems to be that most do not like the rear bar, but for standard suspension, it does tighten it all up and makes the car a little chuckable (less understeer) IMO, but some others recon it is a waste of time.  It all depends how you like you car to drive.....

If you are getting one, make sure you get the LHS mounting bolt thingy... It incorporates the new exhaust hanger, and is unique.... The diff mounts and RHS use readily available bolts and the diff clamps are the same as the front sway bar ones, but the LHS is quite unique....

Escorts don't need them...