The Cardiff branch of Britain's biggest chain has 200 beds in a squat mirror-clad former office tower, right in the city centre. It's not flash, but it's comfortable, clean and terrific value – although you'll need to book early and pay in advance for the cheapest rates. Request a higher floor for a quieter room.
There's no on-site parking, but parking is available nearby at a guest rate of £12 per day.