These appear to be west elm circle cut out chairs. I don't think they in the online catalogue anymore, but I did a quick search and it looks like some sets are coming up for sale on other sites.

I found it here...but God knows how much it's worth... http://www.notey.com/@contemporist_unofficial/external/788254/volver-by-studio-14-for-terzani-raquo-contemporist.html

the verandah is a critical aspect to the original - I'd advise against altering or removing it- it adds dimension and character to the facade/form. I'd recommend any potential alterations/additions (if ever/being entertained) to be contained to the rear and respect/retain existing character that is contributory to the significance of the style of the building. Perhaps consolidate some ideas/goals and then seek some preliminary advice from a professional who is familiar/experienced (and respectful) to the building type you're working with....best of luck with it :) PD

Hi Helen, isn’t it gorgeous? It’s a late 1960s chair designed by Harcourt, model F588 All the best with your renovation, Louise, Decoro Custom Interiors - Window Treatment Specialist, Sydney https://www.artifort.com/collection/model/detail/Armchairs_F587-F588