The car pictured on the front cover of the UK edition of the "Harry Potter and the Chamber of Secrets" is a Turquoise Ford Anglia 105E with the registration number HOW777.
The UK adult version of the novel displayed an actual photograph of a Ford Anglia.
J.K.Rowling arrived in a vehicle very similar to that shown on the cover when she launched the next Harry Potter novel : "Harry Potter and the Goblet of Fire.