Postgraduate loan for university funded student

Hello,
I am a 2nd year PhD student. I am looking at applying for the postgraduate doctoral loan but want to make sure I am eligible.
I get some funding from the university but they have confirmed this is purely faculty-funded internally - they/I do not receive any external funding from research councils/UKRI. I meet all the other criteria. Can I check whether I am eligible please?

Thanks for your help!
One final question - if I initially wanted to request the full amount but later on decide I don't need it all and want to reduce the amount, how does that work? Would I keep the payments already made and the future ones would be reduced? Or would I have to repay some and then the lower amount be split equally for the rest of my course?
I hope that makes sense, thank you in advance.