Can I sue the Dept.of Work and Pensions?

Had an interview under caution in 2007 over alleged D.L.A.fraud,was never told of the outcome.During same interview it was alleged that I had received Incapacity benefit whilst working.Never was interviewed to that effect.During next few years had letters of demand to repay the sum of over � 2600 of alleged overpayment of Incapacity Benefit and stoppages were made from my Incapacity Benefit.Appealed each time.Stoppages were stopped only for a another letter of demand of repayment to arrive a few months later.Finally had a tribunal date in September in 2010and it found in my favour.No one from the D.W.P.bothered to turn up.During the years of calling by phone and writing letters to explain that they must be mistaken all I ever got was that it was on their system and that was it.In November 2010 I wrote to the D.W.P. to ask for a letter of acknowledgement that they had received the verdict from the tribunal.I eventually received a letter to tell me that they don't send letters,but in my case they decided to let me know that they had sent a giro out,but unfortunately to my old address.Have tried to get the money ever since,it's only a small amount (�201 according to them),but one moment a new giro has been activated then it never had and now I will not get anything untill they find the old giro.