mostly Ireland for tax reasons

I tend to agree with that also for US companies. Many US companies already have their European branch based in Ireland. It is closer to US and they share the same language. For middle eastern and Asian, they'll probably go to Germany.

Estonia. All the benefits are with Estonia anyway, UK was just prefered because it sounds cheap at first. (IMO)

I've got a lot of love for Estonia, but you cant really compare it to London

Depends about what we are talking about. Personally i would never consider actually moving to london, but a UK LLC is/was always a option. Therefore thats all i thought about. Local scene is surely a different topic.