I agree with comegetme about getting samples together in the actual kitchen space. The reason why I prefer the lighter one is the pattern. Even though I really like the pattern in the darker one as a single tile, I think that the floor will end up with too many fairly clear lines running crisscross, or if they're laid in the same direction, the lines will never match. I think it would drive me bonkers. Whereas the marble effect tile has a softer and less linear pattern. But it might not be a problem for you :-)

I think it will be difficult to find something to match. I could be wrong but, from the photo, it looks like the drive was some kind of crazy paving made up from broken slabs - 2 or 3 different colours (?) which have since weathered & faded. So if you found something similar to replace them, the colour would most likely be brighter. What happened to the parts of the drive that the builder took up?

Walls and Floors have these https://www.wallsandfloors.co.uk/white-tiles-white-floor-tiles-15072 https://www.wallsandfloors.co.uk/matt-black-white-floor-tiles-black-floor-tiles-15071

It’s common for tiles to be slightly bowed. For this reason this brickbond layout of tiles is very unforgiving for these large tiles because you have lined up the edges that are bowed in with the middle that is most bowed out. Had they been small tiles you wouldn’t have noticed but the effect is exaggerated with large tiles. That’s why the manufacturer recommended an offset brickbond laying pattern. 90/10 would have looked great. Given your efforts to convey this instruction to the tiler it’s disappointing that a professional who should know it’s not recommended to lay large tiles 50/50 brick bond to avoid exactly this situation went and did it anyway. I think the tiler is liable because even absent your instruction he should have known better. It’s professionally embarrassing that he has done it. I think the contractor also shared some responsibility if they hired the tiler. Basically it’s their recommendation, their reputation that is being damaged by poor workmanship and their relationship with you that is at risk. Consider the paper trail - did you get a quote directly from the tiler or through your contractor? It may be that you get nowhere but you should try to get the tiler to accept responsibility. After an firm conversation you need to write to him to outline what you feel is his fault and clearly stating what you expect him to do in return (such as replace all the tiles). You also need to state a timescale for response from him. If you can get it changed on his dime then happy days. If you have to pay for it you might conclude that you can’t live with it. Personally I wouldn’t spend the money a second time myself and I would live with it.