I do believe your correct that they all use the same fuel pump. If not all TFSI at the very least the S3, Cupra and GTi Ed30 all share similar components.
S3 is supposed to have a differing manifold and some possible internal differences compared to the engines used in the Cupra and Ed30. They are on the whole deemed to be identical.
I was told almost 6 months ahead of the Cupra launch by a senior insider at SEAT, that Audi were heavily involved in the engine setup for the Cupra. They claimed that Audi had brought in a specialist team to work alongside the SEAT engineers to setup the Cupra's TFSi engine. Audi are very much at the heart of SEAT management nowadays, the same could not be said 3 or 4 years ago, most of the new senior management in Spain have come directly from within Audi.
Though SEAT have been part of the Audi brand group for some time. It's only in the last 2 years or so, that Audi have taken a firm hand of the brand and are steering it towards being a more sound business.
the owner of the dealer of seat here in venezuela which is a friend of mine told me audi is taking care of seat and is only going to get better from now on which im very happy because im in love with my car and the brand in general