Have you looked at the Hee Barstool by HAY? very reasonably priced and they come in some great colours.

I have lived in two places with breakfast bars in American style kitchens. I found that I tended to spend a great deal of time sitting there so a bar stool with a comfortable back is important. I made mine from pine, copied from some I saw in a bar. I was also given an old captains swivel seat from a yacht so I built a stand for it, reupholstered it and unfortunately left it for the new tenant who liked it. That was one of my favourite seats, to sit in comfort at a breakfast bar rather than balancing without a back to lean on.

Obviously stylish and affordable vary widely for everyone but I always find some great pieces on Wayfair for bar stools. https://www.wayfair.co.uk/Bar-Stools-C1804848.html?refid=GX140235268214.Wayfair+bar+stool~e&position=1t1&network=g&pcrid=140235268214&device=m&gclid=CM_Qr46Lh9QCFdXNGwodKSwE_A Hope it helps!

I've got exactly a 17cm gap between my chairs and kitchen table which I can just about cross my legs at so the gap is fine is to me. Sometimes though visually a stool can look too high. I love LTS's first stool (it's looking good with the bar fitted!) but it looks a tad too high for me personally so it might be good to see a pic of your bar. i may be wrong but think it's going to be hard to find a fixed seat of 70cm. Counter stools versus bar stools come within whatever height ranges and I think 70 probably sits in the middle of those ranges. I've found one stool a bit higher and one a bit lower if they're of any use https://www.atlanticshopping.co.uk/bar-stools/pacino-stool-white.html?utm_source=gbase&utm_medium=se&utm_campaign=gb&LGWCODE=9488;19372;5285&gclid=Cj0KCQjwjtLZBRDLARIsAKT6fXzJSHprROxntwEN9tgd3HHstXnDNUiFpiQBh1pZTWNtT2BvLo__AS4aAgF_EALw_wcB http://www.barstools.co.uk/a-x-bar-stool-white.html