Spot on Jim. I think it's if you have less than a year or there abouts left you can go DD. No other way to avoid it as its a fixed percentage of your monthly.
And Rich, you should be declaring that second income on you tax return then SLC will take the extra from you
+1 Student loan deductions are based on EVERY source of income. Once you breach the threshold, it will automatically be deducted at source. If your main income takes you over the threshold then any other income will automatically attract further payments, that's if your informing HMRC about the extra payments via a self assessment if your not PAYE.
Chris, suck it, you agreed to the T&C's when you took the loan, now pay it back