A seconded position that becomes permanent starts on the day the former position was filled? Any time limit to any wrong doing by my company

My former position as grade 3 car park assistant loading staff was filled in jan 2001. I was seconded to the freight office in 1999. That position was said to be made permanent in may 2001 and I lost the greivance case I raised. Since then I have raised an enquiry as to my former position which I was told was filled, but I could apply to that position when a vacancy arises. I challenged this again in 2002 but was told to "Lump it or leave" by the senior hr manager. I then asked for a review in 2007, by a new manager, but she insisted all was ok and considered the matter closed. I have proof from a letter from hr, stating my former position was filled in jan 2001.