My BMW has the best spare tire in the world: The spare wheel is an OEM alloy that matches the four on the car, as does the tire, a 235/45-17 Michelin Pilot. Any kind of flat tire or wheel damage and I can pop on the spare and continue my journey for any distance at any speed. If the tire must be replaced, it is a standard size available anywhere.
The Porsche has a temporary service spare which must be inflated using a pump prior to use. It has restricted speed and distance limits.
The Mini has no spare. The tires are run-flats, which can be driven on with zero air pressure for a limited distance (120 miles) at a limited speed (50 MPH). Once they've been run flat, they must be replaced. They are not commonly available, especially outside of the core Mini markets (the Northeast, California, and the Pacific Northwest).
The two types of tire problems that I've experienced in my motoring career (not counting delaminating retreaded tires) have been slow-to-fast leaks caused by nails in the tread and catastrophic loss of pressure caused by bending the wheel rim on potholes. The former can typically be repaired, and as long as you keep pumping up the tire, aren't a big deal. The latter, of course, require a new tire and a new wheel.
To make the Mini more useful and usable, and to reduce the chances of needing to buy a new run-flat tire just because I pick up a nail, I assembled the following on-board tire kit:
The items in the kit fit, more or less neatly, in a small bag:
which in turn nestles happily in my newly installed euro parcel tray:
I also purchased the smallest tire pump that I could find, which fits easily in the glove compartment:
I'm going to live with the run-flat tires for a while, but I expect to ultimately replace them with regular tires with better performance characteristics.