“Candidates are asked to enter all their scores for any tests taken when they complete their UCAS application, showing the relevant dates for each. This gives tutors a complete picture of a candidate’s academic record, rather than just the ‘superscore’ of best results for the different sections of any test taken on multiple occasions.”
To get into Oxford you’ll have to be an exceptional student. But math is not going to be particularly important for a student applying for English. You should focus on more relevant subjects, I’m not sure why you’d even bother with a math subject test if you are worried about the score. Better to do more arts subject tests instead. Note also that APs are more highly regarded than subject tests.