If you can make accelerated repayments (i.e. pay more than €336 p.m.) without any penalties (check the loan agreement terms & conditions) then this will clear the loan quicker and reduce your overall interest costs.
I don't understand the point about having taken this loan out stupidly - there's nothing stupid about borrowing money as long as you need to, don't have savings that you could use instead, you can afford the repayments and you shop around for the best deal on offer.