Thanks for all the responses everyone!👍🏻

As usual I think I was trying to over engineer the problem and make it so that an elephant could walk on it but it seems general consensus is that a simple baton running under the stud wall but overhanging the gap with some screws on both sides of the join into the baton should suffice.

I’ll probably still put a couple of triangular wedges in anyway for my own peace of mind as I’m a bit ocd about jobs being solid, but very much appreciated, thank you! 🙏🏻 🍻

So you mean to cot the overhanging section off so that I’m putting the missing piece of floor back in 2 sections?

You may want to reconsider how you try to ‘help’ in future because your ‘help doesn’t seem very helpful. More rude and aggressive.

The OP was asking a legit question and providing information about what they’d been left with from previous owners for context and to aid us in answering the question. Your response was to accuse them of moaning about the previous owner and then tell them they should do a really shoddy job of finishing the room. Also as someone who lives in Europe I can assure you drywall (or plasterboard as we call it) is definitely the preferred finish. I don’t think I’ve ever seen stucco on an interior wall, maybe you’re confusing it with lime?