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I've not actually watched Cutie Honey but I found these two references of what to watch although it's mostly geared towards where to start. https://reasonstoanime.com/2020/11/05/the-ultimate-guide-to-cutie-honey/ https://www.reddit.com/r/gonagai/comments/71et80/cutie_honey_anime_watch_order_recommendation/
It sounds like to me you should go ahead and watch the Original if thats what you're leaning towards. Then you can do Re:Cutey or Shin Cutey (sounds like order doesn't matter between them). I'd assume since Flash is an alternative version you could watch that and the movie after.
I don't know if it's the same for the EU as it is for the US, but Netflix holds the rights for BNA and to my knowledge very few if any of the anime Netflix has exclusive license for ends up getting a western physical release. Which is a shame because BNA and Little Witch Academia are two of my favorites that I want to own, but like you, importing the Japanese releases just isn't worth it. I've not dug too deeply into this so I'm not going to say I'm 100% correct, hopefully someone else comes and surprises us lol