Britain will be better off outside the EU no matter the fees they'd have to pay to trade with US and EU it would be the same the other way around.

Now they are panicking, they even said Britain wouldn't trade with the US if it exits the EU.
Which means also the US wouldn't be able to trade with Britain, just like they don't do it with Russia. And the fees? The super fees Britain should pay, and maybe will have to, for trading from outside the EU? They would be repaid by the fees the Brits would impose for selling EU goods and american ones - if they want them, I don't see the brits, superecologist as they are, inclined to buy hormone meat made in the US -. It would be pretty much like Australia, we italians, if we want to sell tortellini to the Aussie, we have to
  1. Buy the meat by the Aussie;
  2. Open a tortellini fabric in Australia and sell them italian tortellini, filled with australian meat and produced in loco. They are smart.
No, it's the TTIP that would be put in the danger of not existing, unless Cameron and not this obscure Cecilia Malmstrom, signs it, and Cameron is much cleaner and more honest than Malmstrom; TTIP actually discussed in a hotel I was told, the Ritz London, like our politicians are prostitutes who meet their clients in hotels, while these things should be discussed in Parliaments with the conversations recorded or broadcast in streaming, this hotel habit must be prohibited: our representatives are not prostitutes meeting clients secretly in a hotel, they must discuss whatever concerns our society in the democratically elected Parliaments or the entire process be must be declared invalid.

For the rest of the expenses, now Britain, because the fate wants Britain out the EU, was sent another enormous bill by Brussels for the expenses of the crazy policy of Angela Merkel, which is the opposite of the Cameron's government's policy:

Brussels sent to London, the cow to be milked, a bill of 348 millions, yes, I write it entirely in letters so you get it, of pounds because Angela Merkel went crazy and told "everybody come here" and now there's the invasion of refugees and Britain, one of the few countries that took the most sensible decision of not accepting as refugees people smuggled to Europe - mostly aggressive and fit men with some babies in the middle to be used as shield - to stop the practice of smuggling people and now this government should pay the bill for other countries' lefty politicians deciding nonsense.

Bill after bill, it'll be clear that to pay the fee to trade with the EU's countries or to offer separatedly to Germany and Sweden - is Sweden going to stay, by the way? - if we don't pay the fee to trade in your Country you won't pay the fee to trade in ours and do the same for the free movement and it's ok back again.
And if the EU orders the left member states "No, you can't!" ? The EU countries should pay the fee to trade with Britain which will be the same: 5-5=0. Minus the bill to pay for other people's nonsensical overspending - Greece - or lefty refugees/immigration policies - Germany -. I am still convinced Angela Merkel, who was spied on intensely for years, might have been blackmailed to assume this extremely lefty immigration policy and that she should honestly resign. The German didn't vote for the Green after all, the CSU is not a lefty party, they can't open the doors to refugees like they are a no-borders group.

Moreover the "information" that Britain would lose the special relationship with the USA is dismissed with irritation by the american "Brexit will not hurt the special relationship" who said with great respect that it's the Briton who'll have to decide whether to stay or not in the EU and that the person who dared and say "The USA have no interest in trading with single states, but only with blocs of nations" was not entitled to state anything of the kind. 

So, apparently, the Antichrist can swallow its bile. 

You win. If you exit.