Thank-you for your suggestions, gentlemen.
Re Armourer Sergeant Daniel Blackford, I do have a copy of his military service records as well as some original correspondence. The main points are as described in my first post - enlisted at Pimlico in 1861, service in Barbados, Jamaica and Nassau with the 2nd West India Regiment, one year furlough in London, a year at the small arms factory in Birmingham, posted to the Canadian Militia in Montreal, and discharged in 1884. His entire period of service in Montreal was spent on St-Helen's Island where the arsenal and munitions stores were located. He continued to live on the island following his discharge where he worked as a civilian in the Military Stores. Interestingly, he re-enlisted in the Canadian Militia as a quartermaster sergeant in 1903, at the age of 66,and served exactly 3 years - I don't know the reason for this.
As for civilian armourer Thomas Reeves, I have no formal records about his time in the British garrisons at Kingston and Montreal, apart from the birth records of his children and one census entry. He too lived on St-Helen's Island, where part of his house served as the officer's mess. We do know that when the British garrison was withdrawn from Canada in 1870, Reeves moved to downtown Montreal, where he opened a gun shop. His entries in the city directories of the early 1870s indicate that he was the sole agent for the Martini Henry Rifle.