Ignore the 'beware of D platers' bit thats nonsense.
I've owned 3 of these MK4 Escorts.
My D plater had no rot on the front crossmember, the front chassis legs, the front wing i've also seen plenty of other 'decent' D platers.
They all rot including the C platers that the above poster failed to mention, right up until the late builds.
Just go with your head on your shoulders and if you find any rot, consider it and ask yourself can you fix it or afford to get it fixed.
Buying an RS from a enthusiastic like an RSOC member will set your mind at rest as these people care more for their cars than your usual car owner.
But above all you can only trust yourself. A genuine seller will be happy for you to have a good look over everywhere.