I will try to put you in the right perspective. First of all, trying to finance your studies with a 100% third party financing is totally absurd. Since you are interested in economics, simple economics will tell you this is a "very, very high risk venture". Moreover, being a first degree undergraduate will not put you way ahead of other graduates. You should also understand it will give you a head start over other graduates but the starting pay would not be very much different from the other graduates. And you have to work your way up which would take you at least a 5 years period to prove that you are "good material" which is worth nurturing.

You should also bear in mind that an economics graduate from UK will not open many options for you. You are neither an accountant as the most you can get from some of the professional bodies is some paper exemptions. In the UK also, before you can opt to take the Chartered Accountants exam you will need to be a first degree holder first and the big firms there would only consider you if you are first class degree holder.

If you also harbour hopes of joining the top merchant banks like Goldman Sach, Morgan Stanley or Credit Suisse, these firms need any additional qualifications which would require further investments in your education and push you further into debts.

I do agree with the other commenters that NUS would be a much better choice as their qualifications are also world ranked.

Why choose economics and not accounting and finance as the options are much greater here?

Economists merely expresses opinions and they dont create values while finance graduates can identify good investment opportunities.