Had a terrible problem with LHR a couple of years back. Wife broke foot in DXB so needed wheelchair. DXB absolutely fantastic, LHR near complete disaster. According to the person who met us at Terminal 3 they could not take us through Passport Control/Customs. Abandoned us before Passport Control, waited close to an hour, after making several complaints, before someone arrived with another wheelchair to take us through Passport Control/Control. Both wheelchair pushers spoke little English and clearly were expecting a tip, which they never got!