I'd also strongly urge some consideration for Air Canada. I'm heading to South Africa in the Fall (via LHR) and AC had a whole lot more C class available than other *Alliance members (or at least inventory that I could get to with United miles!).

I think there are 3 or 4 flights a day from Toronto and there are also flights from Calgary and Vancouver that might work for a West Coast origination. I think their C class hard product is pretty darn good on the long hauls.