Ah turns out the helperEstimateRelativePose.m script is stored locally with the example but not online. Should be visible at: C:\Users\<username>\Documents\MATLAB\Examples\vision\StructureFromMotionFromMultipleViewsExample
Edit: I also realised that the files only appear locally once the command below has been run. This command is given when the "try in MATLAB" link is clicked in the online documentation (visible when signed in to your Mathworks account).
openExample('vision/StructureFromMotionFromMultipleViewsExample')
The script is also attached, but for the most up to date version use the method above.
