Thanks Fumitani. Its been a good days work. I have managed to reduce the $1,966 to just under $1,000. The main culprits were 2 BA flights and a Qantas flight - the exact same flight under Lan was over $300 cheaper in taxes. itasoftware was very useful in checking taxes for the same flights under different carrier.
I now have:

Cabin Class : BUSINESS

Number of Continents 4
Number of Segments: 15
Number of Stopovers : 11
Routing: KRT (RJ)-AMM(IB) -MAD (LAN) -LIM (LAN)-SCL--SCL(LAN)-SYD (QF)-BNE (QF)-DRW(QF)-PER(CX)-HKG(CX)-BKK(JL)-NRT(JL)-DEL(AY)-HEL(AY)-DXB
I really wanted to get back to London but the taxes for BA flights are extortionate.

Any suggestions for improvement greatly appreciated.



Questions I have left are

1. Does "Canada Pricing" still result in a much lower fare? Online, I have got to $2788 +$1,002 for a DONE4 EX Khartoum. I am in the UK. If Canada Pricing works, what do I need to do?

2. Online, I get all the way to the credit card page for a DONR4 ex Khartoum. Has anyone managed to buy it online? I saw some posts with issues.

3. Which mileage programme should I use for this trip - AA or BA to accumulate the most useful points - I have no status anywhere. I dont have any AA flights as I am skipping North America. Is there a website which will calculate for me?

4. Lastly, I have quite a few stops in Australia - would I do better to fly some of these segments using a low cost airline and save some for say China?

Thanks again. I think I am nearly there.