All I carry for a puncture is my RAC membership card.
Seems sensible, and my wife wonders why I am going to this trouble when all I have to do is call the breakdown service. However, I've always thought it's a bit infra-dig to get someone else to change a wheel. After all, a man's gotta do what a man's gotta do...
Also, in M3Boy's post about Air Seal Product's (thanks for the tip; never heard of this stuff) their website reports that breakdown services are being run ragged by requests for wheel changes (admittedly brought on by lack of spare wheels these days).