I come back to my earlier point. You've been on one overnight, and another one is ahead of you. Both are in J/C. Lying on your back and snoring is not the problem. Jakarta is +/- 13 hours (not sure where he's based) ahead of the OP's time zone. Wouldn't you want to stretch your legs? You're in London after all. Heathrow Express, walk through the parks, lunch at the Ivy, martini at the Dorchester, etc?