Overpayment and PIP

I have been paying back an overpayment from the DWP of ESA via my DLA. I have now transferred from DLA to PIP and been awarded PIP at enhanced rates for both mobility and daily living. I was relieved to get this sorted as I had to go through a mandatory reconsideration and the whole things was very stressful as everyone here will appreciate. Today I got a letter from the DWP over payment recovery section saying that I must pay back approx £180 per month from my PIP I was shattered by this as at the moment I do not have any other income. They said the repayment rate from PIP is a third of the benefit. I explained that I am in dire financial straits and they said they could see if the person who makes decisions would allow me to pay £80 or £100 instead but they could not guarantee this. Is there anything I can do please? Any advice is much appreciated.