It is difficult to go wrong with mandarins at the moment as the late varieties hit their peak of quality from Spain, Morocco and Israel.
The best of the options is the delicious Orri from Spain and Israel, often sold as a tangerine, but Mor (in Sainsburys) is a worthy alternative, sweet, firm and flavoursome.
The other choices are Nadorcott or Tangold, which are also delicious: softer and with a slight tang, but with lovely depth of flavour. Also look out for Lidl’s ‘Pink Mandarin’: a late Sicilian variety called Etna.