Apologies for placing this in the England forum when the first (and only, at this point) Zip hotel is actually in Cardiff, but I figured more people would see it here.
Premier Inn has created a new budget line of hotels called "Zip". From the photos the rooms look very small and as if they were produced out of injection-molded plastic. I think the quarters would be tight for two people to share for more than the odd one-night stay, but as a solo traveler, they look fine to me. I don't care that my odds of a window would be low.
In yet another triumph (not) of the Premier Inn web-programming team, you have to click through to book a room in Cardiff before you see that there is, indeed, air conditioning. There's other useful information there: 8.5 square meters (about 85 square feet, I think), so super-tiny. Just one towel; one hopes they provide a second one if there are, you know, two people in the room. But heaven knows you won't get an answer if you email PI to ask.
This particular hotel looks like it's in a location more suitable for car travelers (though I've only been to Cardiff briefly and could be mistaken); I hope some will be more convenient for people arriving by train or bus.