Maybe I'm now out of date but all the material I've used that contains such images reserve copyright to such photos - I presume you borrowed it from somewhere rather than photographing the actual document which is what the quoted HMSO document implies - if you read the licence that comes with for example CD versions of the census it allows use of the images but not publication - the company producing the cd own (or have licenced) the copyright to that photo - copyright is a minefield just ask any librarian.
BTW there is no need to hide web addresses - this is just for email address to avoid spammers - Google will find your web pages anyway - we block the leading ht_tp portion but you can quote the rest of the URL