And physicists have been writing code for a while simply because the number of software engineers with a working knowledge of physics (as in ready for research

And physicists have been writing code for a while simply because the number of software engineers with a working knowledge of physics (as in ready for research), have been trained in numerical analysis (as in being able to read applied mathematics) and then are willing to help you with your paper for peanuts is about zero. I don't understand why it is so hard to see that you need either a pretty big collaboration where somebody else has isolated the specifications so you don't need to know anything about the problem your code solves really, or becoming a physics graduate student yourself for this line of work.