If you want the seats to swing out from the island be sure to check that the island is substantial enough to take the load, also that the island is well anchored to the floor. If you consider the arm is for example 2 feet long, then sitting on the extende seat will be the same as applying your full weight to a crowbar, two people sitting on one side would destroy a normally constructed island. Similarly, if fitted to a wall make sure that they are anchored well and that the wall structure is suitable. A nice idea to save space though

Depending on what colour your kitchen hardware is, there a couple of options that would work well in a graphite kitchen. If you have white worktops and a grey kitchen, I would add another colour or texture to the stools to create another layer to the scheme. If you don't like using bold colours, you could use an interesting textured metal or wood for the stools. You could try using something similar to the silver wire stools below for a more industrial style Or wooden stools are always lovely for a more contemporary country look. I would use a lighter wood, to add contrast to the dark grey kitchen and white worktop All the best with your project

IKEA Nilsolle

That height should work fine. If you are UK based, can I also suggest you look to atlanticshopping.co.uk for your bar stools? They specialise in them and have a huge range at very keen prices. There is a showroom (Birmingham direction, I think) if you want to see the product. We use them ourselves for the showroom, and many of our customers have used them and been very pleased with quality & value. If you are buying online, you should still have consumer rights which allow you to return product (just the postage cost lost at most) as long as the product is not "made to order" - in which case make sure you are sure before you buy!