More options; use the arrivals lounge as suggested, go & use the facilities at the Hilton by T4. Then go to the lounge in T4. Also consider leaving the airport for a day trip to a nearby town, avoiding London itself - e.g. Oxford, or one of the villages near to LHR. A coach service runs frequently to Oxford from LHR. Other posts I recall in this forum have made suggestions as to good places to visit; I can't remember them off hand.