gap year/defer or foundation year?

i originally wanted to study econ and finance at surrey and was then offered a foundation year as my predicted grades didn’t match what they were asking for
i ended up getting a c in econ, b in spanish and e in maths

i know that maths is crucial to go into this kind of field, so do i defer and find a job/retake maths or do i go ahead with the foundation year at surrey?
i am smart but i’ve unfortunately been quite burnt out for the past couple of years and i couldn’t keep up with the demands of education, so i feel if i managed to find better revision techniques and in a better headspace etc, i could perform better and reapply to better universities