Is a Mk1 cortina axle the same as a Mk1/2 escort axle n so much as halfshafts ,diff etc and can backplates,drums etc be swapped ?..

I think Cortina might be wider

I agree - Cortina axle is a couple of inches wider.

I've just measured mk1 Escort casing across the flanges 48"
mk2 Cortina across the flanges 47 1/2" both without half shafts though I remember the Escort halfshafts were a little too long for the Cortina axle