I'm studying in Wales. I wasn't able to choose the Student Finance Wales section as it does not exist. It should, however. A cursory internet search last night shows that a substantial amount of people have experienced the same treatment from Student Finance Wales regarding money owed. It seems to be that when you owe the system money, they chase you down like a dog -- if they owe you money, they ignore your emails and complaints.
What I'll most likely do is chase down Citizens Advice, or my local MP (probably both!) to see where we go from here. This £90 has been KEPT since September and October, so realistically I should be paid interest on monies owed.