ESO in spain and SIXTH FORM in england

I have a question, did you have to validate your ESO certificate? i want to study 1 de bachillerato because i’m 16 (year 12) in Uk but i did late application, so this year i’ll do the application for sixth form but i have to start fresh year 12 if i had done in Spain? (I DONT HAVE GCSE grades) and all my spanish grades of the last year (4 ESO) is above 7, including physics and chemistry 10. Except French and physical education is a 6 spanish grade that i think that equivalent to a grade 5 or 6.