I've used the Glasgow PEO three times and the experience have always been positive.
Once in 2003 to apply for permit-free training, got it no probs.
Second attendance was in 2004 for the Fresh Talent: Working in Scotland scheme. There was a problem with my paperwork (incomplete evidence), and the checking officer was nice enough to go through the specific documentary evidence required and didn't proceed to taking any payment - you'd have to be seen at two separate counters. One is the document check, and if that's ok, only then would you go the payment counter.
Third was in 2006 to transfer a vignette to a new passport. The staff I'd met were all very professional and courteous. A few were actually quite friendly! But that's Scotland for you. Yes, I'm biased!!
Good luck.