Paperback copies of Bird's novelisation of the series, published by W.H Allen & Co in 1979, still pop up from time to time, although the hardback edition is more difficult to find. For some reason it tends to be more expensive than the novelisations of his other work. A search on the net sites of ABE.BOOKS or ALIBRIS for "Michael J Bird" will usually throw up a copy somewhere for a couple of pounds.
Copies also come up occasionally on e-Bay: Search e-Bay
People often ask me why Bird changed the name of the policeman to 'Mitsides' when he came to write the book (I have even been asked by a policeman named Mitsides!) but I honestly have no idea and neither does his widow, Olive. It remains one more mystery in a very mysterious series.
In October 2012 Bird's son (also named Michael) published an e-Book version of his father's novelisation for the Kindle.
Even though like me you have probably got a copy of the paperback tucked away somewhere at the back of the bookcase, at only £3.99 Kindle owners will agree I am sure that it is well worth getting an electronic copy to while away the odd half hour commuting to the office or to take with you on those long summer holidays. (And after purchasing don't forget to give the book a good review!)