Well I did some remarks for my GCSEs. This how they went:
Maths - 3 marks off A*, scored up to 1 mark off

Chemistry - 1 mark off A*, no change

(my paper was near perfect but my useless and frequently ill chemistry teacher caused me to fail my coursework, something like 14 I got out of 30 :O )
Modern Greek - 1 mark off A*, no change (my school reorder the script and couldnt understand why I didnt get 100%, so I retaken the damn exam this year)
History - what a surprise, 1 mark off A* - my coursework was at 100% as well.
But guess what? The remark gave me 14 more marks, giving me nearly 95% overall! 13 of those were on 1 single question.
I'd say it's with getting remarks, what's a hundred quid for the safety of your medic career? And if you're poor, get the school to give you a bursary.