The blend word frenemy will most probably come in handy more and more in discussing post-Brexit relations:
friend + enemy = frenemy
Here is its entry from the Oxford Advanced Learner’s Dictionary online:
This word is actually not anywhere near as new as Brexiteer and Remoaner: its first use is recorded as being in 1953. But its usage has increased in recent years.
The big band of Brexiteers includes many frenemies: people united in their wish to leave the EU but otherwise with different political views or social backgrounds. In the situation in which the UK will be cutting at least some ties with old friends, it will need new ones – and will most likely have to make some frenemies too! Which countries will prove to be lifelong friends, and which will become best frenemies remains to be seen.
For more entry to Oxford Dictionary check: https://oxfordlearnersdictionariesblog.com/2018/04/01/brexiteers-remoaners-and-frenemies/