You need 100 hours post-PPL before you can do your night qualification so, if you did your PPL in 55 hours or less, you'll be OK to do that before you start a CPL course. You've also got to find an airfield that is open late enough - most people wait until the clocks go back.
If you're an R22 chap, then Aeromega at Cambridge or Central Helicopters at Nottingham.
Cheers
Whirls