I couldn't find any details about the pamphlet on-line, except those in the two library catalogues I cited.  I consulted the Australian National Library's copy and took a photocopy of it (24 pages).  I also tried poking around the Historical Association's website without finding anything relevant.
I have withdrawn my suggestion that Russell's description of the pamphlet was inaccurate.  The Historical Association apparently updates some of its older pamphlets occasionally, and it could well have done so with its Common Errors in History (although I have no evidence for that, other than Russell's description itself).  I did try browsing through the Australian National Library's collection of the  Historical Association's later pamphlets without finding anything else relevant.  But since the National Library's collection is incomplete, that doesn't mean very much.
It might be worth contacting the Historical Association itself to see if they can provide any further information.
— (talk · cont)