Shall I get my GCSE Chemistry paper remarked, or not?

I really wanted an A but ended up with a B. I guess I was content with the grade at first but now that I have gone back to school, I found out that I scored a UMS of 315 and an A grade was 320. My teacher is considering whether to get it remarked. I got an A for paper C1 C2 C3 a B for paper C4 C5 C6 and an A for my controlled assessment. I did the OCR Gateway Chemistry GCSE course incase you're wondering. Also, how many more marks do you think I will need to pick up in order to achieve an A grade or in other words how many marks is 1 UMS worth? Thank you in advace,
Katie :/