Innit is not British for desu goddammit! Desu is a formal Japanese declarative, it just means “is” (not exactly but close enough). Whereas innit is just a contraction of “isn’t it” which has a completely different meaning. For example, take the phrase “It’s a bit far”. In Japanese this is “chotto tooi”. If we add “innit”, this gives “it’s a bit far innit”. The innit signifies that the speaker is seeking affirmation, akin to the phrase “don’t you agree?”, although in this case it may be said rhetorically. However, adding desu to the Japanese translation gives “chotto tooi desu” which is COMPLETELY different. Not only is there no seeking of the affirmative (in fact the speaker would just be declaring the matter to be known outright), appending desu actually makes the phrase formal! This is literally the opposite of innit, which is generally seen as a very informal thing to say. A far FAR better translation would be “janai”, the Japanese equivalent of “isn’t”. When used at the end of sentences, this can be thought of to mean “isn’t it” and hence can be used in place of innit for almost all use cases. “chotto tooi janai” is a far better translation of “it’s a bit far innit” which matches both the level of formality and the affirmation-seeking tonal nuance. Sometimes “darou or deshou” is more appropriate. But desu is rarely the equivalent of innit.