I’m applying to many joint honour maths courses like maths with finance or maths with actuarial science.
But my personal statement is just based on maths and not on the joint honour subjects. Is that ok? Will I still be considered
It's not ideal. It depends how competitive the universities you're applying to are - it would certainly harm your chances for top unis like Warwick or LSE, as they really want to see your passion for the particular course you're applying to, and have enough applicants that they can pick people who seem the most interested in the course.
Both departments will look at your PS, so the finance/actuarial science departments can veto you getting an offer, even if the maths department likes you.
It's not ideal. It depends how competitive the universities you're applying to are - it would certainly harm your chances for top unis like Warwick or LSE, as they really want to see your passion for the particular course you're applying to, and have enough applicants that they can pick people who seem the most interested in the course.
Both departments will look at your PS, so the finance/actuarial science departments can veto you getting an offer, even if the maths department likes you.