The Brazilian equivalent of EC261 is ANAC400 which unlike 261 applies to all flights into or out of the jurisdiction (as opposed to 261 which doesn't cover non community flights flying into Europe).
Previously I stated that the ban on surcharges which is covered under ANAC res 138 is on flights out of Brazi, however now I'm wondering if it's the same scope as ANAC400.
I have sent the document to a friend whose Portuguese is much better than mine to see if it is clearer on scope.
Ultimately if ANAC res 138 is of same scope as ANAC400 there should be no YQ on any flights to or from Brazil including LHR-GRU. As BA have a history of being liberal with it's interpretation of this law, this is definitely worth exploring.

ANAC res 138 below.

https://docs.google.com/viewerng/vie...Q.pdf&hl=en_US

Update:

The wording is that the scope of this is any travel originating in Brazil, or any flight operated by a national or international carrier flying both domestically or internationally. My friend says it isn't hugely clear, but her interpretation of it is that it covers both flights into and out of Brazil.