The very best way forward is to go to your nearest (or preferred) flying club that conducts flying training. Explain your situation and they should sit down with you and tell you exactly what you need to do to get back in the air. Basically, get a medical. Then you need to find your old licence, show it to your chosen training establishment.. They will then conduct 'Training as required', then you will do a Licence Proficiency Check with an examiner. Complete the paperwork to convert your old JAR licence in to a Part-FCL licence. You will hear a lot of strange new terms (like Part-FCL!) but it will all become apparent in the end. If you're quick, you might even be able to get your old IMC rating back, now quirkily referred to as a IR(R).
Good luck and welcome back.
TOO