The hours which you have logged already will indeed remain valid towards your PPL - if you've kept your logbook as proof, of course.
You will need to re-sit the PPL ground exams and to fly sufficient hours to meet JAR/FCL requirements before you can take the PPL Skill Test. But you'll get 100 hours theory credit towards mandatory CPL groundschool time if you pass your exams successfully.
For the JAR/FCL PPL, basically you need:
1. To pass all the exams
2. To hold a JAR Class 2 medical certificate
3. 45 hours as pilot of aeroplanes, including 25 hours dual training plus 10 hours supervised solo time, of which not less than 5 must be cross-country including a flight of 270km in accordance with JAR-FCL 1.125(b).
4. To pass the PPL Skill Test (which is included in the 45 hrs total time requirement).
Best of luck!