I have no experience with this, but I don't see why it would be a problem.. A lot of students in the US take 4.5-5 years to complete their undergrad degrees, so I don't see why it would be a problem. I'm purely guessing the US Stafford Loans don't fully follow the UK Education system, so they won't realize that you're repeating your second year.
Also, I don't think the UK student loans system even has a problem with students repeating years, as my DB switched courses after his first year, and had to start from Year 1 again.
I think the main thing to be concerned about is the deadlines for getting the loans. I can't remember when it is...