dd had one totally random paper - B3, which was 70 UMS (right on the B/C boundary). The other 8 science papers were all well above 90 UMS. That took her biology grade down from A* to A. We decided in the end not to get it checked or remarked (risk of it going down to a C) but have asked for a copy. DD has no idea what went wrong & I'm intrigued to see it, she's never had a mark anything like that low in biology 
Her school had an amazingly good year, their overall five 4-9 including maths and English was way higher than last year. Girls did really well - dd was 5th overall, two girls got three 9s & there were only two boys in the top ten.
I was so stunned by her maths result that I impulsively gave her £50 - I'd taken cash to school & budgeted in case we needed remarks - she's spent most of it already ... cider for parties, a giant shark, junk food & a computer game. She told me that one of the other kids had said he was going to get nearly £1000
for his results. I don't know if that is actually true but it would buy a hell of a lot of cider!
She's at Reading now, I'm shell shocked by the whole thing - thank god we don't have AS levels next year.