You really need only 1200 TPs for Gold, yes. If your last flight on your LAS itinerary was when you already reached Silver status you can make a call to BAEC explaining that you want them to take this into account to calculate when you qualify for Gold (if you do). You need to keep an eye on it yourself though and call back when you have reached Gold in your mind. Sometimes they also reinstate them on request, or so I've heard. If your last flight earned 120 TPs whilst you only needed 40, than you can kiss the remaining 80 goodbye though.

Oh, and where are my manners? Welcome to FT and BAEC!