Hallo again Sid
Confess I haven't seen the title you refer to, but I am very certain the type in question was NOT developed as a dive bomber as such. All light bombers are designed to be capable of "diving", the Henley as well, but that is a far cry from the "true" dive bombing we have come to associate with the JU 87 (mode initially developed by the USN). The specification for the Henley was that it should be capable of diving, but I have seen no specific details as to what angels etc this specification refered to.
What I am very positive about is that it was not the diving capacity that killed off the Henley as a bomber (diving or not), it was the changed climate in Europe. I am in agreement that the Allied Expeditionary Force in France would have been better off with the Henley than the Battle, but that was hard for the "thinkers" in the 1937-39 period to anticipate. I doubt Britain and RAF in particular had a scenario even coming close to what actually happened in the 1940-45 period and although Britain came out of the the Battle of France as "second best", the rest of the war proved those planners slowly fought their back to to the top
Cheers
Stig