so the Friday 1pm UTC time simply sucks for us, as we are basically missing half of the team...

I think that Tuesday 7pm UTC would work a lot better - please reply to this email with your opinion and availability for this time.

Example reply: "I like Tuesday 7pm" or "I can not attend on tuesday 7pm" or "I can attend, but i may have some other meeting at work on tuesday and may be late..." etc etc =]