[jpblue1000]

James,
short answer is everywhere!
Long answer is also everywhere but common areas for the Mk2, are similar to the Mk1;
front floors
sills
front wing supports
rear tank well and spare wheel well in boot
bottom of doors
base of windscreen
boot opening top edge
base of rear window
heater bubble base
front bumper iron mounts
A pillar to weather strip
A pillar around door hinges
C pillar vent is very common in mk2 as are rear wheel arches
base of front guards behind wheel
inner splash panel
Remember they are circa 40 years old poorly designed and built cheaply by drunk people.
Pop across to some of the popular 'escort' sites for detailed photos of rust

JP