Originally Posted by
Passmethesickbag
SK will steer you towards the LH lounge at LHR. I would recommend giving yourself plenty of time before your flight, and braving the hike through the tunnel to the B satellite where you can have a drink in the stunning UA bar and then move to the SQ lounge for the terminal's best food, before you need to walk back to the A terminal where most SK flights depart from.
For breakfast timing I like the Air Canada options better than the Singapore Airlines options. I have yet to test UA. Despite what people say, I don't find the walk between A and B that daunting.