Transferring to LSE from Canadian university

Hi! I was wondering if there are people who succeeded in transferring to LSE (preferably Economics or political science) as a 2nd year student from McGill, U of T, Queens or Western?

I could not find lots of info from the internet so I would love to hear advice from those who already experienced this. 

I am assuming when applying for the transfer I need to apply in the same program as I studied before. However, I know that UK schools have strong Economics program, meaning that if I major business or other subject in Canadian uni, I would not be able to apply to the Economics program since I am in different program. Is this true?

Also, can you guys tell me the transferring process and how I apply to it?

Do I need to make a UCAS account same as the people who are applying to the freshman year? Would high school grades matter and would it be considered the same as those freshman applicants or would uni gpa only matter?

Also, I would be so thankful if I get more advice and if you guys share the experiences !

Thank you:)