You can ask for your test to be remarked and I believe you used to be able to see your paper with a head teacher and warms person ( but not sure if can still do this since CEM ) tests. Speaking as a teacher, the problem with many clever children in maths is, under pressure they don't read the question, for example, a question that states there are 10 books in a pile and each book is 3 cm thick, what is the distance between the 1st and last book, many children will instantly put 30 cm and come out saying maths was easy, many will take longer and get answer right or will have practiced this type of question with their tutor (so prepared for it even if not overly clever on maths), likewise the verbal reasoning a cloze test may say he reached the s..m.t of the mountain, but under pressure puts summet, they get no marks even though new the word. Many many clever children do not get the score they deserve on the day due to luck of the questions, more tutored kids who have practiced up to 4 or 5 papers a day, silly mistakes, pressure etc. Its not always fair and probably best to move on and watch them get a string of As in whatever school they choose if they are bright kids.
With the new testing procedure it's very unlikely there would be any change to a child's score following a re-mark. I'd also say there is no chance whatsoever of seeing a test paper. Answer sheets maybe, but that's about it.