I voted 18:00 GMT a few days ago. But I think I'd actually prefer 17:00, or even 16:00, since I've already got another couple of regular tournaments at 18:00 on Sundays.
19:00 would probably also be good. But no later, since some of us have to get up early for work on Monday.
19:00 GMT = 20:00 BST = 21:00 CET (and 15:00 EDT), so it sounds a lot earlier than it actually is for a lot of us. (During daylight savings, anyway.)