For Birmingham Conservatoire and the Royal scottish is there a time allocation for length of pieces?
or is it down to common sense?

Does everyone get an audition if they have applied to a conservatoire

For son's RCS cello audition they have asked for 2 contrasting pieces, total length not exceeding 10 minutes, not sure about Birmingham, will have to look up.

I would think that all conservatoire applicants should be offered an audition, unless possibly it was obvious from the application that they would not meet the minimum entry requirements?