Just to add to your remarks on re-marks in Gloucestershire (!)- it was certainly the case three years ago that a parent could request a re-mark; there was no charge for it and it was jolly quick. However the caveat was applied that should the mark go down, the lower mark would stand. It was also mentioned that only once in living memory had a mark ever been changed.
The official guidance this year, produced in an uncharacteristically funky font on the GCC website which is sadly not reproducable here, states:
Papers are marked twice electronically by computer and manual checks are also carried out. It is highly unlikely that an error could be made in the marking of the papers. However, parents/carers can request a manual remark of their child’s test paper as part of the appeals process.