What is your actual Maths GCSE grade? Contextual offers can mean a lot of things and even if you are eligible there's no guarantee your GCSE requirements would be lower or not scored, if that makes sense.
You will really need to go over every university's website as they all have slightly different criteria, but it sounds like you would likely meet them at many universities. While some will require you to have completed a summer school, many will also give extra points in scoring or a guaranteed interview, but not a reduced offer. That could help compensate for a lower GCSE grade as well at some schools.