They're government.
Yeah I will do the income-based if I have to. Would really like to refinance though...
If you're receiving funding via US based Federal loans, then any repayment you're going to do in US dollars as well, right? Why not try entering your income as USD on these applications(because than your income would be higher)? The UK government uses the OANDA currency converter; you
could enter your income after converting it this way. The dollar and the pound don't fluctuate that much.
If you're being paid in GBP, then I think converting what ever amount you make monthly/Weekly/ etc. is a reasonable way to go about it.
https://www.oanda.com/currency-converter/en/?from=GBP&to=USD&amount=1But this really depends on whether you're going to do automatic payments from a US based account, or are going to transfer the funds via a wiring service, or if you're trying to pay directly from your account in the UK.
I've seen Transferwise mentioned (a wiring service), which is one I also use and would recommend.
Personally, I think your best option is the income based repayment. Start making some payments; when you've crossed the threshold you need to for refinancing, do it.