The title in question and a genuine one. I'd question why a member would go to the trouble of having a 'Head Observer' title privately made when they were very short lived and replaced upon the designation 'Royal' to the Observer Corps. Also the BD is 1943 dated and the trousers 1942 dated. The ROC came in to being in April 1941, so even adding the title straight away, it was attached to the BD at least two years after it became obsolete. Added somewhere along the line to bump up the price, especially considering the rarity and value of the title?
http://www.monsmilitaryantiques.co.uk/viewphoto.php?x=2