I'm in a similar position to you (missed an A* in Edexcel Eng Lit by 1 mark when I was getting straight A* all throughout sixth form). I never even questioned getting the A* because I'd been so consistent and was happy with the papers. I also seem to have had a very harsh examiner as I got 36/40 on one of my papers and 33/60 on another when the quality of response is very similar.
Have you requested your papers back and read your responses again? I would highly recommend — you'll be able to tell if thes examiners were along the right lines or completely off, as I feel mine were. If they're willing, I'd also recommend asking teachers to read your scripts over and give you their opinion on them.
5/6 marks are generally considered a lot to gain for remarks but it's definitely not impossible, especially for humanities. People have gained more from them before and personally I think I'm missing at least 10 marks. I know this is a really stressful/annoying situation but you should absolutely still feel proud of yourself and take comfort in your knowledge of your own ability. I'm sure you'll have a great time at your insurance and, if the remarks yield the results you need, you could always try ringing up your firm and explaining the situation to them? Best of luck!!