Thanks @Pstork1,
So, to give a little more context, the update item action updates the link column to the file in the doc-lib, in the following format.....

once the list item is created.
I went down this route as the file gets moved to a different sub-folder after an approval step. I haven't found a solution to be able to maintain file ID consistency as the file moves to a different folder the ID changes, and thus unable to update the list item with correct link.
So, although your suggestion works when i copy the file link from the doclib and add the section - &action=default&mobileredirect=true - to the end of that link, the true link (code) changes once moved to another folder. The only thing that i can see which is consistent is the filename which is why I am using the update item action as above.
Interested to know your thoughts on my method and if you have any other suggestions?