I have answered at Local moon or international moon? .
I add here about your example. See these maps: http://moonsighting.com/1434shw.html .
As far as i understand these are visibility that was at sunrise or sunset... to celebrate at august 8 in UK there should be new moon at sunset or sunrise of august 7 seen at proper location on earth.
New moon was firstly visible with optical aid at august 6 21:50 ut
at location souther than Australia. What time was there? it is at +10 hours, so, there was 7:50 of morning of august 7.
Also it was later visible with naked eye at southern america's morning of august 7. it is at utc-5, so, it should be 14:50 at uk at that time, if sunrise was also at 7:50, but i see from a map http://www.timeanddate.com/worldclock/sunearth.html?day=7&month=8&year=2015&hour=10&min=50&sec=0&n=&ntxt=&earth=0 that it was nearly 10:50 of august 7 at uk at that time.
So, maybe, it, new moon time, was said about green zone, and it was 18:50 at south america at that time, and i see in stellarium, that new moon is visible at sunset. so, i was wrong, thinking that new moon is not visible at sunset on southern hemisphere.
as it was well visible at sunrise of august 7, august 8 can be counted as eid. though, btw, it could be visible badly at sunset of august 7, because moon was not visible at northern areas, and i think that it should not be visible at equator areas, because moon sets almost at same time with sun there, though some mountains could hide sun earlier in some places, and moon sets earlier than sun in southern hemisphere, so it is not visible at sunset there.
As you can see at http://www.timeanddate.com/worldclock/sunearth.html?day=6&month=8&year=2013&hour=21&min=50&sec=0&n=&ntxt=&earth=0 , at evening of august 6 at which new moon was in south america, britain had passed sunset, and it should not be counted for britain, but new moon of august 7 should be counted, and eid at august 8, (i think that if new moon is at sunrise of august 7, it is too late to count august 7 as 1st day of new month).
Is there logic in celebrating Eid at August 9? - If visibility in other place is counted, then it should be celebrated at August 8. If only local visibility is counted, then new moon is visible only with optical aid and only in southern part of UK on August 8, and it is visibility at sunset of August 8. Since it is bad visibility, and only in part of UK, and if criterion is that there must be local visibility in every location, then Eid should be better celebrated at August 10, with that logic.