Minor detail but did anyone else notice they are using eu-west-1? Kind of weird for the UK to be hosting there sites in another country (Ireland). I'm sure this isn't super sensitive data but still.
They've been on AWS since before eu-west-2 was added, it's still not at the scale of eu-west-1. Capacity issues are still a thing (but getting much better), and only recently have they become pretty much feature parallel.
I think one of the bits of carry-over legislation in the Withdrawal Agreement after Brexit was the UK continuing to comply with GDPR. So using an Irish DC is still ok.