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

Don't know about your budget or style. These ikea ones are super cheap and have washable covers. These velvet ones would look fab but not so practical!! You could also consider wood to add some warmth to the room and easy to clean. http://www.ikea.com/gb/en/products/chairs-stools-benches/cafe-bar-chairs/henriksdal-bar-stool-with-backrest-birch-ramna-light-grey-spr-79214357/?cid=gb%7Cps%7Cpla%7C%7C%7C%7C https://www.atlanticshopping.co.uk/bar-stools/marco-oak-stool-grey-velvet.html https://www.coxandcox.co.uk/weathered-oak-stool

Hmm... I think I've found the legs, but think the back shapes are different. Anyway, have a look: https://www.diningchair.co.uk/-/bar-stools/

I think the kitchen layout is great, however instead of a traditional hob on the island, I would personally opt for an induction hob/cooktop. That way you won't have to fear that your children will accidentally touch it and burn themselves (read how induction cooktops work). It's also completely flat unlike traditional hobs, so when you are looking at the kitchen from different angles, you won't even notice it, and when you do, it's just nicer, it's just more modern and elegant. I've also seen induction cooktops designed for islands, instead of the traditional 2x2 arranged in a square, you can find one that is rectangular, all 4 circles in a single line, and I think those look great. Also they have some that have built-in ventilation (that goes into the island), so you won't need a huge exhaust hood above the island in the middle of the kitchen. Also I've noticed the design on the sink, and I personally think that that style of sink takes up a lot of space without providing too much function (I've had it in my previous home). I would 100% swap it for a double sink, it takes the same amount of space, but it's so much more useful and convenient.