Reviews might not look for extra marks, but often when the review of marking is carried out, errors in application of markschemes are identified or the examiner reviewing thinks a question has been out in a wrong level, which means there is a change. Essentially, the impact in some cases will be more marks and possibly a higher grade. Obviously when errors in marking are identified on papers which were close to the next grade boundary, going up a grade is easier to achieve and that’s why it’s still when it’s most applied for.
Yes, in majority of cases the marking is accurate and no change. However, a decent number change.
The other thing to ask for is marks in the 2 or 3 papers to compare. Big anomalous between them if a kid thought it went well can also indicate it’s worth going for.
Sometimes it’s 30 marks down to the grade below and only 1 mark to the one above. the chances or dropping 30 marks are incredibly tiny. A lot of it will come down to if you want to spend £38 or whatever your Board is on a bit of a punt.