£7.60 is illegal. The minimum wage for someone over 25 is £7.83. Not a lot of difference sure, but still illegal. (I'm assuming you are in the UK as you are using £, and over 25 as you describe yourself as a mature student)
I suggest you read this, but bear in mind this is the minimum legal wage. What is a good wage, I can't help you with other than to say an illegal one sure isn't.
And yes, your employer would be responsible for any tax under the PAYE system used in the UK since 1944.