How does this compare to other students in your high school? Your grades will be interpreted in the context of the high school or national system that you are studying in. For each of the schools that you apply to, someone on their staff will be familiar with the grade scales typically used in Singapore. I am not.
Are you applying for the Lester B Pearson scholarship at Toronto? You need to get your high school to nominate you for this, and it is exceptionally competitive. However, I do not see how it would be affordable otherwise.
I also do not know how UBC would be affordable with a budget of US$20,000 per year.
And I have no idea whether financial aid is likely at the schools in the UK.
Affordability might be just as much of a challenge as being accepted.