With TWR/APP ratings in the UK you can go to almost any UK airport, with the UK AREA rating you can go to either Prestwick or NERC. Whichever of these last two you go to you will, most likely, stay for life.
With AREA rating you can go to Bahrain, UAE ACC (not recommended) or Muscat. With TWR/APP ratings you can go to almost any Gulf region airport.
Is AREA the same as enroute?
In terms of your interest to overseas areas / opportunities to move etc, what is the difference between tower, terminal approach and en route?