Need some serious advice!!

im 19, year 13, living in leeds, its nearly the end of the year, ive taken maths, photography, art and resiting english gcse because i dont speak english very well.
I GOT 4 OFFERS FROM huddersfield uni for architectural technology, interior architecture from harrogate college, architectural technology from leeds met. but suddenly we decided to go to london so the offers wont be any use for me.
i admit i didnt put much effort this year, i was lazy as ****.
i want to do architecture at uni, but i dont feel confident about the exams,
so i wanna redo the year 13 but this time put everything i have on it. studying hard, getting A grades, but i wanna take mechanic as and a2 aswell because i think the architecture course requires maths and mechanic
do you think its a good idea? or is it just wasting time? what do you think i should do?