Transit Permit from Japan to HK through Shanghai

I hold a UK passport.
My one-way flight is from Japan to HK via Shanghai.
Later I will be booking another one-way flight from HK to Guilin or Xian (not yet decided) for which i will anyway take a Single Entry Visa into China.
The wait in Shanghai for the first flight is about 19 hours.
Would the Transit permit be enough (for the Japan to HK via Shanghai) or would i need to gain a Double Entry for this?