Hi Vatsal

You should take  SAT - Scholastic Aptitude test along with very good +2 scores especially in PCM for engineering.You should also take an English test,either IELTS or TOEFL.

After you have all these in hand apply to foreign universities in London and try for scholarships.

Fees is 24 lakhs for studying in UK , it can be even more expensive for London specifically. Living cost is around 10 lakhs.

Hope this helps!