Rather than carry a mobility kit to deal with a flat tire, it is possible to retrofit a space-saver spare wheel and tire under the boot of some models, a complete list of which can be found on RealOEM. Parts Diagram and List
No Description Supplement Qty Part No 1 Spare Wheel Carrier 1 51717184110 2 Spare Wheel Hub Cover 1  3 Spare Wheel Bracket 1 51717124365 4 Protection Foil 1 51711510375 5 Spring 1 41117044685 6 Spring Guide 1 41117044687 7 Cover 1 51716800127 8 Handle 1 51718165737 9 Threaded Bolt M10 1  10 Hex Nut M10 1  11 Hex Nut M6 ZNS3 3 07129904868 12 Plastic Nut (for coarse threaded pin) 1 16131183133 13 Plastic Nut M6 2 16131176747 14 Hex Nut AM10-8-ZNS3 1 07129904864 Spare (Emergency) Wheel 15x3.5 ET35 1 36111509164 Tire 115/70R15 90M 1
-  Included with Spare Wheel Carrier (1)
- Parts pre-fitting:
- Open the boot of the car, lift up the carpet and remove the MINI Mobility Kit or whatever may be in the cut out in the floor.
- This should reveal a rubber bung and 3 rubber covered studs.
- Get under the car and remove the undertray next to the exhaust which is held in place by 2 nuts in the rear and 3 screws in front.
- This should reveal the under side of the rubber bung and 3 foam covered studs facing down.
- Remove the rubber bung and stud coverings inside the boot and then secure the Protection Foil (4), Spring (5) and Spring Guide (6) to the threaded studs with the 3 Plastic Nuts (12 and 13).
- Remove the body protection foam from plastic studs under the car, being careful not to strip the threads.
- Secure the Spare Wheel Bracket (3) to the 3 plastic threaded studs with the 3 Hex Nuts (11).
- The Hex Nuts need only be tightened slightly more than "finger tight".
- Place the space-saver wheel and tire over the Spare Wheel Carrier (1) and position it under the car.
- Attach the Handle (8) to the Spare Wheel Carrier (1) through hole in the boot floor and pull it up so it clips into the Spring (5).
- Secure the Spare Wheel Carrier (1) in place by fitting the Cover (7) and using a wheel brace (lug wrench) to tighten the Hex Nut (14) on the Threaded Bolt (9) of the Spare Wheel Carrier.
- Admire the result.
- Photos courtesy of RedMiniOne1
- The fitting instructions above can be used for the early style Spare Wheel Carrier.