I'm pro EU, I'm not British, but it's too early to say.
My guess is that Brexit will be somewhat bad for Britain, but not majorly so and Britain will cope just fine.
The main way Britain could lose is from a geostrategical point of view and regular citizens don't really care about that (until it's too late). But who knows, maybe the "Special Relationship" will help.
Switzerland, Norway and others not in EU, do profit from the "Special Relationship", with the big difference that it was organized from the beginning and their governments actually had a plan.
A plan that was not "let's screw the EU from the inside to our advantage".
Can't find that interview from a Norway official or EEA representatives that basically said "Hell no, we don't want you to screw up our relationship with the EU like you did. You are toxic.".
I wonder what polls are saying about how Europeans see the UK right now.
edit2: just found again this interview https://www.youtube.com/watch?v=VtNr4z3YrYo in which Farage says the UK will be (I think he meant remain) a member of the EEA on Brexit day. It didn't since they were only member by virtue of being a member of the European Union.
Nor did I said they were, rather Switzerland, Norway and others (too lazy to search which ones I still miss) governments, managed to negotiate their position with EU to their best interests.
It's not neccissarily "their best interest" for one as there is no objective "best."
A key difference is that in Norway and Switzerland the "political elite" is pro-European and often wants closer ties up to joining, in UK however the brexit is the culmination of a decades long "RU/Europe/Brussels is evil" campaign and the British government gives little reason for the EU to believe in good reason for their negotiations.