Yes they (Cadburys) will melt... from recent experience. Put straight in a fridge upon arrival... or eat.
Cheaper brands seem to fare better... probably because they're full of lots of 'other' stuff.
Coming from York (with its huge chocolate factory... Rowntrees, now taken over by Nestle), as I do, I can tell you that chocolate destined for hotter export markets such as the Philippines is made to a different recipe and also has different packaging.
Just try to keep it out of the sun and then into a fridge or aircon room, and all should be ok though. It probably won't be sitting around for too long.