There have been posts in the BA forum (tried to do a search, but couldn't find them) whereby somebody purchased an ex-EU fare (ex-EU are generally always cheaper than ex-LON on BA, even though ex-EU transit via LHR), did not travel on the final LHR-(somewhere in Europe) sector, and was stripped of the entire BAEC points for the flights actually flown.

The basis for this (according to BAEC) was that the contract was to fly (using FRA and ORD as examples, but not too sure of the exact details of the situation) FRA-LHR-ORD-LHR-FRA, but by flying FRA-LHR-ORD-LHR, which was a higher fare, the passenger was in breach of the contract, and therefore no BAEC miles were payable for the entire journey.

Opening this up to others who may have read the thread (damned if I can find it) but it might be an issue, and something to be considered.

Dave