the path to ucl is full of uncertainties...
it's hard for an international student to work there...the company will need to do a lot in order to hire you..there's a chance if u are really good in your field..

however go to nus is way safer...the tuition grant, financial aids...of course it does not offer as much as uk does, but still it is a highly-developed country..you can move to uk if u wan after graduate in sg..

i think jpa does offer some sort of Ivy League scholarship, isn't it? don't know the details though.

i know giving up a UCL offer (and the experiences it brings) just because of your financial problem sucks. but rm400k debt after graduate, while you don't even guaranteed a job in uk? you shouldn't take such risk.