Perhaps that didn't actually answer your question, so let me also add that all student loans are written off, no matter the outstanding amount, after somewhere between 20 and 35 years depending on which country of the UK you're from and when you were at university. For myself, for example, I entered a university from England in 2008, so I will pay back for 20 years following graduation in 2013, assuming I earn more than £17,775. Which, as a PhD student, I don't. So I'll only end up paying off the loan for at most 16 years, and in 2033 the rest should be written off. Meanwhile I've been accruing interest at a rate of 1.25%, so the amount I "have" to repay has been rising steadily. Obviously I've no intention of telling you how much that is but the main point is that unless I earn something like £100k annually then I don't think I'd ever repay the full amount.
Alternatively, my brother, who started after 2012, will only repay once his income goes above £21,000, but picks up far more interest (current I think it's about 5% = inflation + 3, but I'm not sure how it's calculated), has a higher total loan to repay, and could expect to be repaying for up 30 years, ie until 2047. Again, I'm not going to share more than that information for obvious reasons, although I will say that he's rather a lot more hacked off about all this than I am.