You don't need to rush this. The Night Rating is only required for CPL issue, not prior to your skills test. So don't worry about it. Finish your course and when that's all signed and sealed, then worry about getting the right number of whatever hours the CAA require.
Plus, you don't need the night rating issued prior to the application for a CPL, only to have completed the training. Saves a few pennies that way round.
I'm surprised your CPL school didn't mention any of this. Odd!