If you ring or email the admissions team there they will tell you the furthest distance offered. Someone did this last year and posted it in one of the discussions about secondary admissions. I can't find the post now, but from memory it was 1,050m. That, I think, was "safe walking route". I believe that this year they are switching to "as the crow flies" distance. You're best to ring and ask them, but I'd leave it until September if you want this year's distance as I think you still get a lot of movement all through the summer holidays, right up to the start of term.