Sometimes a slipping or juddering Clutch can be effectively cured, by just replacing the Clutch springs, assuming that all the plates and friction discs are in good shape.
To ensure you order the correct number of springs, and for any other Clutch parts that you feel you may need, check out the online 'parts list' fiche for your model. It will help you assemble a complete 'shopping list' and avoid ordering an odd small item at a later date that may hold up your work in progress!