it changes slightly the working frequencies. 80hz instead of 100hz, or 5khz instead of 12khz...
its just a different way to eq. you could say that "british eq" does not exist.
During the 1980's and 90's less expensive products began to show up from other parts of the world.
"British EQ" was thus coined as a marketing term that became used by many companies to combat less expensive products.
they felt that by making the distinction that not all mixers and EQ circuits sound the same they could maintain market share even at higher prices.
and the idea worked because there is still today quite a bit of mystique around the concept of "British EQ", as if it was some sort of "magical cool-sounding" tool.