Yes. You did an assessment paper, to see what course you should be put on. But that doesn't give you any evidence or qualification at Level 2.
Most colleges get students to do simialr assessments if they don't aready have GCSE at C or above - I used to run a Maths and English department in an FE college.
If the college you are at do Functional Skils they can show you were al the test papers are and you can have apractice, then they should be able to be flexible enugh to arrange an exam for you - they are online and run all the time, the exam officer just has to arrange it - which can be the sticking point as it can take the same number of staff for a single person as for a room full of students!
Nonetheless you can be entered for and take the exam without having to attend classes, if they agree to accommodate you.