Porcelain is a tough tile which will not crack or break easily. they are very long lasting. vinyl is out dated and just doesn't look good. Your other option should be ceramic tiles. So it should be between ceramic and porcelain. I'd still recommend porcelain but ceramic is cheaper, that's the biggest advantage of ceramic. I bought these porcelain tiles two weeks ago, they look lovely. beautiful hexagon porcelain tiles

A picture would really help! A large landscape mirror is a good bet in narrow hallways, as long as the frame is not obstructive. A dado rail will help break up the height (so giving the illusion of more width), and allows her to paint a bolder colour below the dado without making the space too dark (white or off white above the dado). Maybe even a picture rail too. She could use satin eggshell under the dado, it’s tougher and more easily cleaned than emulsion, and also has a sheen to reflect light. A large coir mat near the front door, spanning the full width of the hall, to help keep things clean and also reduce the visual length of the hall (to help it look wider)

That's interesting colourhappy - we did omit the aqua tiles and put just the taupe with blanco (which has some grey tones in the variations) but it looked a little bland which is why we thought the aqua might liven it up but now I'm thinking you are right and they are too cool for the flagstones.

B&Q have some nice patterned floor tiles. Here's a couple I think would go well with white wall tiles.