Hi Chloe welcome to S.O.C
I Don't see a remap helping unless you have some other mods added to the car that should have had a remap. If you can get the codes read from the ECU should give you a code and tell you what is at fault, it could be anything from very small to maybe being big :( Hope its just a simple job :) And I wouldn't worry about the mileage as long as it's been well looked after not thrashed everywhere oil changes done I can't see it being a big problem :)