Steve,
I would be interested in hearing more about a kit for repairing big gashes. I did see an interesting demo at the Top Gear show in November where you pre-filled the tyre with some liquid which immediately seals any holes that appear. He was doing impressive demos with a knife and screwdriver repeatedly stabbing a tyre filled with this stuff. He did say that the lowest profile you can use is 35, which is right on the limit.

Has anyone got any experience of these sorts of solutions ?

cheers

Paul