DLA underpayment recovery moved to IB & faster!

Due to my own error my benefits were overpaid. This was sorted out last year and agreed to be deducted over 18 months from my DLA, and would have been due to finish repayment in mid 2012. Last month I had a letter saying it was now all coming out of my IB and was now being taken out by October this year. I can manage the money, but should I be worried about my DLA or is there more here than meets the eye? I was told that they had had 'instructions' to do this.Anyone else had this or am I being paranoid?

Deductions can be made from most but not all social security benefits in order to recover an overpayment.

It is however unusual for the deduction to be changed from one benefit to another during the recovery process. Accordingly, it would be interesting to know what 'instructions' were issued, and by whom? Furthermore, the DWP should have adequately explained their change in position whereby the recovery was transferred from your DLA entitlement to IB. In the circumstances, you may wish to seek an explanation for their decision?

Insofar as you DLA award arises it would be unlikely that it would have any impact on your entitlement, but an adequate explanation from the DWP as to why they have changed their position may allay your fears?

Thanks for the advice.
I wrote and have had a reply .
I am advised that the reason for the change is due to a 'change in policy and they are now required to deduct from the main benefit in payment' OPAC - (Operational Policy Advice & Correspondence team are apparently the authority behind this. Apparently this change is to recover overpayments as economically and quickly as possible. Fair enough. Stating the obvious 'any change to the rate of deduction will have an affect on the period of recovery' - no really!
I received an apology for their not having written to explain and give details.
All in all no great progress, but at least I have a paper trail to which I can refer if anything else changes. I hope I wont need it.