Very Basically UK Licences don't exist any more. The European JAA licence is what you will need. In order to instruct you must have a minimum of a JAA PPL and have passed the JAA CPL written examinations. If you wish to be remunerated then you will have to acquire a JAA CPL. (25 hour flying course + flight test)
Once you have that, you can add the FI Rating which requires at least 15 hours flight training and 30 hours ground training plus a Test.
Essentially the only credit you receive is for flying hours.