Well it depends where your from aswell. Me being from america and there is such a small NA playing base. Most NA tend to play in the evening/night american time (sorry i dont know GMT times.
).
Well here are some of the popular NA servers i know of.
/N/Servers: (CTF)
/N/CTFinsta
/N/ R&R (Rocket and rail mod)
/N/Jewctf (a joke name
)
**::FF::Femmes Fatales**
Digichalk (FFA)
Ciggaweed (FFA)
Here are some of the EU popular servers im aware of (All of the following are CTF.)
Evil|Insta+Rj (rocket and rail mod aswell)
ROFL Instantgib!
3w clan insta
supeR, CTF
supeR, Instantgib
I'm sure there are others. These are the ones that i know of cause i play on.
Just remember the EU player base is much bigger than the NA player base.