Gwyneth Paltrow had her earphones in as she and husband Chris Martin landed at Heathrow airport on Friday. The couple arrived back in London in time to celebrate Gwyneth's 38th birthday today! The actress has been getting back into the school routine with her kids, and she'll soon be showing up in a new classroom when she guest stars on Glee this season. Ryan Murphy revealed she'll be playing a substitute teacher whom Matthew Morrison's character falls for and she'll be singing three or four solos on the episode. The heavy song load shouldn't be any problem for Gwyneth, who has belted out tunes on the big screen before and will once again showcase her voice in Country Strong.