If the author died in 1946 then copyright in his works expired at the end of 2016. The work is in the public domain. The relevant section of the Copyright Designs & Patents Act 1988 extends to the whole of the United Kingdom, but not Crown Dependencies or colonies.
You need to be sure that the work is the author's own work. If someone else has contributed then the copyright endures until it expires 70 years after the death of the last of the authors.
The same applies to art. If you want to reproduce artwork, say for a cover/sleeve design, that would also have the artist's copyright, which lasts for 70 years after that person's death. The typography of a book has copyright which lasts for 25 years from publication.