FARMA rules are based around 5 major principles:

Food must be produced within a defined local area, usually 30 mile radius of the market.

The food must be sold by someone involved in production.

Primary produce (things that are sold without significant preparation) must be grown or reared locally.

Secondary produce (value added items, for example pickles or bread) should contain at least one primary product from within the local area, with a recommended minimum of 25% local ingredients.

Traceability: Information should be available from the market and the traders about how items were produced.

As an additional quality safeguard, UK farmers' markets have to abide by regulation from their local authority, and some local authorities including Warwickshire have adopted the FARMA guidelines as a requirement. So you can be assured that produce is of the highest quality and provenance.