I think the more choices the better. I'm not against the UK having their own exchanges. I'm against the UK leaving the Erasmus program. The UK already had exchanges programs to go to those countries that were not part of the Erasmus like Australia/Canada/Japan. The problem is cutting the Erasmus.

Also in my experience students that wants to go abroad will go nevertheless the location. When I applied for the Erasmus there was only 1 spot in the whole UK at the Glasgow University. A student with better marks than me got that one. I got my second choice which was Bergen, Norway. It was the best time of life. Leave the students the opportunity and let them know they have those opportunities