haven't got the TAP for Glasgow, but ....
...is the MSA definitely the SALT, don't MSA's only have 1000' clearance? Possibly the SALT should be 1000' higher than the figure you briefed.
AND
what is the teaching at the school? If they teach use the highest MSA regardless of the arrival sector, then that's what you should do. If, however, they teach use the most appropriate sector then you may have a case.