I'd like to do the following starting next January

1) Mid-January - Fly New York to London to Edinburgh (2 weeks in Edi)
2) Late-January - Fly Edinbrugh to London (1 week in London)
3) Early-February - Fly London to Delhi (2 weeks in India)
4) Mid February - Fly Delhi to Beijing (3 weeks in China ... overland to South China)
5) Early/Mid March - Fly from South China to Bangkok (spend 4 weeks in Thailand, Cambodia, Vietnam ... I can get to these places via AirAsia)
6) Early/Mid April - Fly Bangkok to New York (1 week in NY)
7) Late April - Fly NY to Lima (1 week in Lima)
8) Early May - Fly Lima to Buenos Aires (2 weeks in Argentina)
9) Late May - Fly Buenos Aires to Edinburgh (3 weeks)
10) Mid June - Fly London to New York.

I believe I should be able to do step 1 and step 10 as a single Round-Trip ticket, and then steps 2 through 9 as a 4-continent RTW ticket via on OneWorld (Europe, Asia, North America, South America ... in that order). I've heard that it is cheaper to book a RTW starting in the UK rather than the US, which is why that would make sense. Is this true? Does my plan make sense? Does anyone know how much this should cost, and whom I should order through to get the best service?

Also, I would have liked to be in South America before North America, but I dont think there are flights from Bankok to Lima or Argentina that do not stop in Australia. If I am wrong please let me know.

More generally -- What are peoples expirience using OneWorld for long trips of this sort? How early in advance should I book?

Anyway ... please help, and give any advice you have on booking this