Importing photos but insufficient space

I keep running into this problem when I try to import photos from my SD card to my iPhone.

I always get the error message that there is insufficient space, x.xx GB required.

My phone is set up to optimise storage and offload to iCloud. I am already paying for the highest available tier and I’m only using about 10% of it.

The storage information in Settings says that I am using 30.4 of 256GB

I’ve seen other responses to this question suggesting offload apps or deleting songs, movies, etc. No one has ever given a useful answer.

i don’t have any movies and the songs are less than 5GB. The only thing that can possibly take up all this storage are the photos that I’ve been taking while on holiday. I shoot in RAW mode so each photo is about 35MB - iOS only supports my camera’s raw format in uncompressed mode.

I can see that photos are being uploaded to iCloud when I open the photos app, but after everything is done the space is not reclaimed, despite the os reporting that I have over 200GB free.