My apologies if I am not posting this in the tight place.

What sort of fares are "companion fares" offered on with American Express Platinum? Don't want to end up paying some badly inflated price when I could get two consolidator fares cheaper.

I am looking for Virgin Upper Class (or Continental BusinssFirst codeshare on the same flights) tickets for LHR/LAX around the Christmas period (probably out on 26/12 and back on 07/01, but dates flexable at the moment). Do Amex offer the companion deal with these airlines? Are there any blackout dates?

I don't have a platinum card at the moment (would only pay the increased membership fee for the companion fare offer) and can't seem to find much information out on this offer.

Thanks,
Boo