If I'd choose an european country to found my startup, it would be Estonia, they have a system in place, called E-Resident that anyone can apply to, and get "citizenship" so after that you can create your own business along with a bank account there, all online.
If you are European and have a bank account in your homecountry, from what I've read you don't even need to fly over to Estonia to get that bank account, the bank will accept that. If not, that's the only thing you really need to go to Estonia.
Historically yes, but the fallout from Brexit may make London a vastly less attractive option, causing it to lose its spot in the years to come. I honestly can't imagine starting something new in London now -- it's very expensive and it has some big political and economic uncertainties hanging over its head at the moment.
