Regardless of how I feel about LHR (not much), and even if everything goes right (planes on time, reasonable crowds, etc.), sometimes 2 hours and 10 minutes may still not be enough.

If it were me, I would build in a "fudge factor" to cover unanticipated headwinds, tailwinds, mechanicals, weather, terrorists, unruly passengers, volcanos, strikes, fog, pestilance, famine, death, heart attack, BAA staff working to rule, or just plain bad luck.

A quick check shows another 4 non-stops after 8:30, and before 12:30, plus a handful of connections. It's not like you are catching the last helicopter out of Saigon.

Plus, if you take a later flight, according to Murphy, the earlier connection will go off with the precision of a fine Swiss watch.

Plus plus, if it were me, with the extra time, I would go on a "LHR lounge crawl." ^^^^ (one for each lounge)

Whatever you chose, via con Dios.