If you're dead set on becoming an actuary, 100% actuarial science is the best. It offers exemption which enables you to start a career right after graduating. Sure, you could do a maths degree but you'll be 8 exams short. No employer will hire an actuarial graduate with no exams taken. The key thing here is only if you sure you want to become an actuary. If you're still not sure then perhaps going into a Maths degree will be better for you.
But don't let that put you off. An actuarial science degree is very much highly regarded and is not wholly subject specific to being an actuary. It gives you a very strong background in finance, maths and many others. If you choose a uni with a good range of electives, you won't be disadvantaged at all if you decide becoming an actuary isn't for you and you can still be in a very strong position to find non-actuary jobs. You should look at CASS in City university of London for the course as well. They offer a good mix of both theory and practical applications for the course,, something like other unis (LSE) do not do.