I need some advice. I'm in a lost situation...

I am currently in a lost situation because I am not sure if I should stay in Korea and attend international school or move to UK to study A levels. My grade is currently 11th grade and turning 12th grade soon. In order for me to go to UK schools I need to get the visa (obviously). However, in order to get the visa I have to take english proficiency exam. The options for english proficiency exam in the visa requirements were PTE, IELTS and TOEFL. I already booked PTE exam because PTE exam result comes out in 2 in days. Yet, the school in UK said they want IELTS. If I do IELTS it takes 2 weeks to get the result and visa takes 3 weeks, which makes me to miss the school for a month. So right now Im in a lost situation. (PS. I already interviewed with the UK school and they wish me to attend their school as well.)
The reason why started to consider moving into UK school is because I plan to go to university in UK. With A levels it will be easier for me to go to UK universities as they prefer A level scores. Also, my family is currently in bad financial situation right now. I stayed at international school in Korea from 9th grade to 11th grade. Their tuition fee is 30,000$ and 20,000$ for dorm. On the other hand, the UK school that I'm trying to attend is one third of the tuition fee.
Will it hurt if I miss first month of year 12 A-levels? What should I do?

You need to speak to the UK school. IELTS is probably your only choice, so get it booked asap. The school will also have a view on whether missing a month isa problem - it probably is, but it depends a little on the school.