Although hinges may appear OK they may well need replacing as springs do gradually fail. May well need new runners (the mechanism that hinges locate into) as well as bearings can also fail.
elux hinges generally £30 for a pair if not obsolete! – worth a go as P45 said tho – PNC/Prod no/ or PR No. for a more accurate quote. 9 or 11 digit code that will start with a 9XX XXX XXX (XX) usually located printed between the model number and serial code! hope that helps!