No you shouldn't need the dash for the mk1. The body control ecu ( bcu) General electronics module ( Gems ) as its also known does the alarm ect.

The bcu does see the pats signal but I have swapped ecus before with out swapping the gems unit. Ive played with a lot of Ford ecus but because I take the engines out of the donor ive never really played with the gems.

Does the ecu have the same four digit code ?

And the rfid chip really does have to be be in the perfect place and not just close by.