Trying to put a little cinq back on the road although tatty it seems solid now . It started our as a 899 but I got it as a 1.2 8valve project one fault though is I cannot get the 5th gear. Is it a cable issue if they are the original 899 ones ? or a gear box fault ? any suggestions

Pretty sure that at least one of the gearbox cables is different, so that may be the issue. They're not cheap, so scrappy may be the best solution. AFAIK, Sei Sporting and Cinq Sporting are identical.