Considering I know very little people in the GMT-1 - GMT - 3 zone or inbetween, 8PM gmt sounded fit to me, not too late for most people up to timezones of GMT+6, VERY early morning for australians, and maybe just the time americans exit school, and maybe even work.
For most europeans the timezone is simply fit. Seeing as the server is located in Europe, the likelyhood of more europeans playing is present.
In either case, to confort australians and americans, doing one at 1AM GMT would be a reasonable idea too.