Sorry when I said tag it onto CPL training I didn't mean to suggest that it could be done as part of the CPL - I meant that when you're at your training provider do 5 hours at night when you won't be CPL'ing.
If I recall correctly you only need the 5 hours night for CPL issue. You don't even need the 'qualification' in your licence, just do 5 hours at night. Therefore you only need to have when you're at the point of applying for the licence.
Nobody's suggested Inverness - maybe a bit far for you and even less dark at this time of year! Even at Pik there might be local restrictions on circuits beyond a certain time - I'll check.