I'm not terribly familiar with your system....ours is slightly different but as i understand it, your jurisdiction and ours granted a level 4 to start with under grandfather rights to all licence holders. it is (here anyway) valid for i think three years ..and if one is going to any renewal in that period you can ask for (in your case you can download the form and take it to an examiner i think) and get the test...and get the amendment to level 6...which is for life.....
in your jurisdiction persumably it is similar because i was contacted today by four CAA PPL holders who want me as an examiner to complete the form for them to enable them to get level 6......
but as i say...i think i read somewhere that your system was a little different to ours...