There is no evidence that 4 RWF ever had a history written about them (the best account of 4RWF is in 'Red Dragon' by PK Kemp and John Graves). Similarly, and officially, 7 RWF never had a book printed on them, but a privately printed one did appear titled 'The Seventh'.
Philip, The 4th gets several mentions in the book, The Astonishing Infantry The History of The Royal Welch Fusilers 1689-1989, by Michael Glover. ISBN: 0 85052 2544 Regards Tom
To be brutally honest I found that book (despite both authors previous work being exemplary) sadly lacking, inaccurate, and frankly tripe in regards to NWE compared to the earlier 1950s book by Kemp and Graves. Hence I don't really recommend it. That said some of the stuff in it on Burma is rather good, but again original history is far superior.