Regarding taking exams early....
At DD school there was a chat about it. If DC brilliant at one or two subjects but doing less well at other subjects they encourage them do the exams early. The rationale is that they can get the easy ones done and then concentrate on the ones they find harder. End result is that they get higher grades across the lot BUT the Really good Unis know this and it doesn't demonstrate the DCs ability to cope with a high workload which is REALLY important for higher education.
So in essence they are only encouraged to take exams early if there is a risk that they could get low grades at the other exams. It's a balancing act.....
They also do a selection of igcse and gcse because the igcse tend to have their exams earlier so the exam season is spread between 2nd May to 13 June in DDs case (MFLs will still go for another week after this date). Art was end Apr.
DD goes to an independent so they know how to play the game!!
Sos - reading your previous posts it looks like your DgD is good at all subjects so you def made the right choice to do them all at the end (even if it doesn't feel like it right now).