I want to replace my brake light switch due to it having a fault code on it (00526) and from searching have seen there's an "updated" switch. Could anyone tell me what I am looking for, or what the ECP link to the right one is?
TPS or audi dealer mate is the best bet... there won't be a choice of switch it will always be the latest revision... chances are you won't get an 'updated' switch from somewhere like ECP or GSF as they typically sell pattern parts... VAG revise certain parts over the life of the part for various reasons... typically due to problems during service so revised parts normally have a different letter after the part number (although this is also used to designate a model variation too such as colour etc)
Get it from a dealer then you know its the right part... they are not that expensive IIRC...