I asked around the Maritime research community on this issue and no one can find a vessel named PURDY.
Spindler, describes the incident as a gunnery action that ended when darkness set in. U 95 maintains contact, and then sinks HOLLINGTON during a submerged torpedo attack.
I need info from U 95's KTB to see whether the submarine attacked one steamer or two during the gunnery phase of the engagement. If it's two ships, the obvious answer would be that PURDY, whatever her true identity is, took a shell hit which killed Thomas Heron and three others. If U 95 was in action with a single steamer, then either PURDY is another name for HOLLINGTON or the PURDY/HOLLINGTON link was false and Thomas Heron was killed in some other action.
I will look further in the British sources at Kew regarding this incident and make a further post with my findings.
I believe we owe it to those who were killed to at least get the correct name of the vessel they died on.