Since you did not hold a night qualification at the start of the CPL modular training then as far as I am aware JAR-FCL requires that the CPL flight training include 5 hours night training.
Thus I believe that you need to show having completed this training for the CPL application. Perhaps the school at which you trained in the US would certify that the night training they completed was in accordance with their CAA approval and complied with JAR-FCL. If you can do that but the PPL night training was completed some time ago, you may be required to repeat the 5 solo take-off and landings again - no problem if you are already night current!
PS every JAA country requires the night training for CPL issue unless you already hold a PPL with night qualification so the CAA are not any different.
Regards,
DFC