Once again, thanks for all of the help!.

Seems this routing may be the best I can come up with:

DONE3
cmb-xsin-lhr-ist-xlhr-mct-xlhr-yul-mia-xdfw-sjo-xdfw-sfo-jfk-xhkg-bom-hkg-cmb

DONE4
cmb-xbkk-xlhr-dxb-xlhr-ist-lhr-yvr-xdfw-sjo-xdfw-sfo-jfk-syd-akl-mel-per-nrt-hkg-sin-cmb

CX office in CMB wanted an itinerary before they would give me a price for a DONE*

I have emailed the above to them and see what they tell me. Hope the price difference between DONE and AONE isn't too much.... Might be able to do it in A which would be better with the big intercon trips.

Thanks again.

BTW- what do you think of the value of the Circle Explorer fares for 3 or 4 continents? I assume that they are considerably cheaper, but using Africa, one could maximise mileage, and visit some interesting places too.

Something like this:

(3)cmb-hkg-lhr-ist-lhr-cpt-jnb-hkg-cmb
(4)cmb-sin-lhr-ist-lhr-cpt-jnb-syd-hkg-cmb

Both satisfy the places we have to visit, though the 4cont. would be much better, taking in Australia. If it is a lot cheaper, we may consider this.