Ruth Davidson who is the Scottish leader would be the best choice as Scotland is where they gained rather than lost seats.  Boris Johnson despite his buffoonery might do better in urban areas as they took a big hit in London and his plain spokeness might allow him to do better in the North which voted heavily leave but generally goes Labour.  If Labour had Owen Smith or Sadiq Khan as opposed to Corbyn they would be on their way to winning instead of tied or just slightly ahead in the polls.  Corbyn is very popular amongst millennials who weren't around during the 70s and 80s, but scares the heck out of most over 55 including even many traditional Labour voters in that age group.