Help with travel agent please

The Oneworld Global Explorer (not the Oneworld Explorer) includes services of all the Oneworld airlines (including all the Lans in South America) but also Air Pacific, the Fijian airline. The GlobEx is mileage-based, so you can't go as hog wild in route planning as you can with the OWE, but if you rely on a couple of budget flights in S. America (to conserve miles) you could go from London to Brazil to Argentina to Peru to Chile to Easter Island to Tahiti to Auckland to Fiji to Samoa or Tonga, back through Auckland to Hong Kong and down to SE Asia, before returning to London, all within the allowable mileage. If the mileage is too much, you can break the trip at Hong Kong and fly budget airlines around SE Asia, before returning to HK and returning to the UK.

If you want to start in South America (i.e. pay your own way there) then you'll still have to end in SA, so probably cheaper just to start in the UK.

Look at oneworld.com for details.

A lot of travel agents will have trouble helping you if you don't have a fairly clear itinerary, which may be a large part of your problem. If you have specific legs and dates of travel, you'll get a more interested response.

Another potential issue is that you generally can't backtrack. If your goal is to travel westbound, then you must consistently travel westbound, without reversing direction at any point.

I would suggest that you consider doing a hybrid version, using a RTW ticket to travel between the various continents and islands, and making separate arrangements for travel within each region. For example, rather than use the RTW to travel to all of your destinations within South America, just use it to arrive in one South American city and depart from another, and sort out the travel within the continent itself by other means.

To add to #2, once you get to the region if you aren't keen on going overland or buying flights there you can often get regional air passes. There's a South American one you could look at.