Presumably by merit of where you are now, you already have the necessary skill to autodidact your way to the equivalent of a comp sci MSc
Read the Kleppmann book on distributed systems - that is probably worth an MSc in itself.
Read the CTMCP book - probably worth another MSc. (PL theory)
What do you want to specialise in ? Choose one or two topics and look at the curriculum in a few universities. What books are on the reading list ? You can likely learn far more self-studying the material than any lecturer will be able to transfer in a few hours of tuition every week.
A comp sci conversion degree is probably close to worthless at your stage, and a more specialised degree still of questionable value considering the cost.
My anecdotal data point of 1 - I don't have a cs degree but work as a highly paid senior contractor on interesting problems, using functional programming to build distributed systems. Early on in my career I read an undergrads worth of text books, and then followed it up with several masters level textbooks.
The best devs I have worked with are constantly reading comp sci text books or papers. The knowledge has a much longer shelf life than x new framework or y new library.
All that said if you want to do it for some intrinsic value then never let anyone talk you out of pursuing education. I just don't think the degree will make much difference to your career, it's the knowledge, confidence and ability to demonstrate & implement that will give you access to better opportunities.