No they can't, pension payments can't be reduced or stopped to recover past overpayments.....
But Yes They CAN, It actually happened to an EX Friend of Mine who got Overpaid,But Did get it ALL Taken back off him FACT !!
And did you agree to pay them back, you can say no, they can't take!....But....They CAN & WILL Take it out of any future Pension Payments they make to Him.......
It wouldnt surprise me if you'll need to be resident in your home country to receive these kinds of pensions...Yep, The DWP Have said That I Have " LOST " My Residency Status,But That Doesn't Stopp you getting a State Pension as they were " Hinting " That's According to Mr. Google anyway.....
Lucky man - at 81, I only get 102 GBP per week State Pension frozen at this rate for the past 16 years!...Yes He IS,I Only get 72.00 Pounds a Week which has been frozen for 11 Years....Fortunately I have two other pensions that are index linked.I Don't So Your Lucky Ain't You ??