It doesn't work like a debt though. Okay I might owe the university £30,000 but I only pay anything back once I earn above a certain amount so I'm never going to be struggling to make payments because if I don't earn enough I don't have to make the payments. Plus after (I think 30) so many years the "debt" is wiped anyway.

If the uk decided tuition fees were now £1,000,000,000 a year then the only difference would be super high earners would be paying off the loan longer. Nobody would be struggling to make payments, by contrast if the US made tuition fees $1,000,000,000 a year then every single student would be unable to make payments and go bankrupt.