Airlines like Thai can be wonderful or horrendous. I've had SQ & MH make changes they didn't have to by simply being nice.
If you find yourself at Heathrow staring at a long delay to Copenhagen, with the possibility of missing your connection, i'd suggest trotting over to T3 and speaking with Thai Airlines to see what they can do - either delay your flight for a day, or even look at flying you out of Heathrow. And smile and some warmth can make wonders happen.