Upgrading existing doors with varnish for 30 minute protection (building regulations for extension)

[Guest Paul]

Hi there, 

We are looking to source an effective and affordable solution to upgrade 8 doors to give 30 minute fire protection and meet building regulations, would you be able to advise on where we can source these products, please (are there local, retail or other sources other than the found/contacted Rawlins and Property Repair Systems)?
Many thanks (before I go ahead with one of these).

[AnthonyB]

These are the most well known manufacturers of such products: https://envirograf.com/product-category/fire-doors/

[Neil Ashdown MAFDI]

Not all doors can be upgraded to 30 mins by painting though?  The product data sheet for the paint or varnish should provide details.