My building inspector has told me I need a national class 0 rating for spread of flame on a cabin...

It's important to ensure compliance with building regulations and standards for fire safety in your area. Class 0 rating for spread of flame typically refers to a specific fire resistance classification in the UK, indicating that the material has undergone testing and meets certain criteria for limiting the spread of flames and smoke.

In terms of European standards, the equivalent classification for fire performance is typically categorized as Euroclass ratings, ranging from A1 (non-combustible) to F (highly flammable). Euroclass A1 is the highest level of fire resistance, indicating materials that do not contribute to the spread of fire.

To determine the equivalent Euroclass rating for a Class 0 fire rating, it's best to consult with local building authorities or fire safety experts who can provide specific guidance based on your location and the applicable building codes. They can advise on the appropriate Euroclass rating required to meet the equivalent level of fire safety standards for your cabin roof construction.