I think Casio calculators are quite popular in the UK - I used an fx570 through secondary school and university. It was the one recommended by my school, and then it was one of the three models (all Casio) allowed by my university[1]. I briefly had a TI83 for A-Level Further Maths, but I didn't use it much.

The fx-9750 would have been usable at secondary school (though it's more powerful than what you really need), but it wasn't on my university's allowed list.

[1] Currently you can use an fx 991, fx 115, or fx 570 for CS, and I pretty sure the list was the same whilst I was there - https://www.cst.cam.ac.uk/teaching/exams/calculators