disco 2 rear seat wont stay up !!

The rear seat on my disco (the bench seat) wont stay up. The pull up button dont seem to do it's job.I took the side panel off and the cable is fine.The small spring inside looked stretched so shortend that'still no good tryed givin it all a good spray,no good.Messed about for a while and the spring pinged off.Where to ? who knows! Obviously will buy new spring but not convinced it's that.It doesn't seem to engage properly.
Anyone know what to do before i take it to bits and pull my hair out??