Shortly after the war, he joined the British Royal Navy and advanced to the rank of rear admiral, before his retirement in 1968.

On learning of the 1939 invasion of Poland by Nazi German forces, Iskra returned from the Atlantic and left two crew members with the ship in Morocco.

Along with the rest of Iskra's crew, Bartosik boarded a French ship and departed for France, where after deliberations between the French Navy's War Department and free Polish forces, he reported as a member of the reserve officer group at the ship-base ORP Gdynia in the United Kingdom.

Bartosik helped to carry Red Cross supplies to Norway and Denmark before Conrad was returned to the Royal Navy in September 1946.

His draft to Anson was nearly rescinded when her captain noticed that Bartosik dared to sport his Polish Virtuti Militari ahead of his British DSC.

From 1964 to 1965, he commanded the guided missile destroyer HMS London, and from 1966 to 1968 he was Assistant Chief of Naval Staff (Operations), with the rank of rear admiral.

Having sacked his second-in-command in the newly commissioned guided-missile destroyer London in late 1965, he was sent the strong character Mike Henry as a replacement.