For low amounts which need to be easily accessed, Premium Bonds may be a way to go. They're made by the government under NS&I and works a bit like a lottery (although you don't lose money "buying" tickets, each bond you have is worth a ticket and there is a monthly draw).
Essentially you set up an account and invest money in them. Instead of just your money gaining interest, it is put in a pot with all the other bonds and that money makes interest. The interest earned is then shared back to all the investors through the monthly draw. You can win £25 up to £1M (and there are millions of prizes each month), even if you only have a bare minimum investment (although obviously putting more in gives you more odds of winning).
It does fall slightly behind inflation and you can go for a few months without winning anything, but it does give the possibility of making a larger return, albeit by luck, compared to other investment opportunities. If you're done with it, you can just access your funds and take them all out again with no questions asked. It's low risk, but that means that the rewards may be lower too. If it's a student loan, which you need to live off, then safe investments are clearly going to be a good idea.