Originally Posted by lowlander
...I am told that I cannot have more than one stopover in the same city. Is that correct?...
It is not correct. There is no 'one stopover only' rule. You can have more than one stopover, the exact number depending on other rules.
...Is it OK to use other BA flights, paid for separately, during a stopover period?...
Yes.
Do LHR and LGW count as one for stopover purposes?
Yes.
...Are overland (or other carrier) transfers to return to a stopover point allowed. In the route desribed above, I would arrive into Manchester, but depart ex LHR...
Yes, surface sectors are allowed, subject to other rules.
I called BA to ask, and was told to call Trailfinders as they seem to know the rules better than BA!!
Perhaps you called the general BA number, not the RTW desk? In any case it is not surprising, the OWE is quite a beast when it comes to taming its many rules. I suggest you take a look at the sticky above, the one with the FAQ.