Q: Warranty if iPhone purchased abroad?

The iPhone warranty is not and never has been international. The "exception", if you want to call it that, is phones purchased in the E.U., which is considered a single country for warranty and service purposes.

No clue how the Brexit is going to affect this. I haven't seen or heard any statement from Apple regarding this yet.

Then what you're referring to is not addressable here. That's a legal question that does not involve Apple's warranty at all. Ask a lawyer.

It seems to depend on each country whether the second year will be honored.

Reading through a few of the Warranty terms for different european countries, Spain and Germany specifically state 24 months of warranty coverage.

The Netherlands does not go beyond stating a "reasonable time".

For the first year you should have no issues getting warranty service in Europe in any country.

For the second it will depend on the Country you wish to get service in.

http://www.apple.com/legal/warranty/statutoryrights.html

I suggest you read the terms for each country, as yes the second year is dependent on the specific countries warranty laws.

I suspect that any statutory rights granted under the law would be limited to the country of original sale, as I don't see how one country could impose their laws on a seller in a different country... And I suspect that Apple, like most companies operates as separate legal entities in different countries.

I suspect as much as well. Though Apple in one country that has the 24 month warranty law, may in fact honor such warranty from another country with a similar law.