The UK will either have to pay a fee to access the EU market, as Norway does, or pay trade tariffs. I find it astonishing that anyone believes that a country can have free access to a trade bloc without a quid pro quo - especially when that trade bloc will have an incentive to "encourager les autres".
Iceland trades tariff-free with the EU without payment of fees.
Turkey trades tariff-free with the EU without payment of fees.
Tariifs work both ways.
If the EU insists on charging us tariffs to trade with them, we charge the EU tariffs to trade with us, after all they sell us more than we sell them.
Outside the EU we will be able to trade with the rest of the world without paying the EU to allow us to do so.
Having the 5th largest economy free of EU control may encourage the Norway and Switzerland to re-examine their own trading relationship with the EU. Switzerland has just withdrawn its application to join the EU. Norway has invited us to join them in EFTA.
Tariffs - if they are imposed, which I don't believe they will be, don't scare me at all.
It would also probably need to compensate farmers, and replace EU funding for research.
There is no such thing as 'EU funding'. The money is EU member country money that has been handed to the EU so the EU can rebadge it as 'EU money' and pretend the EU is being bountiful. The EU, not the sovereign Governments, decide how the money is awarded.
The EU is an unnecessary overhead that reduces the money that individual member Governments could be giving directly to their own farmers and scientists. But the EU is not solely about trade, it is also a means of transferring the wealth of rich member countries to that of poor members countries. Sounds great until you realise that poor old Greece was allowed to max out on Germany's credit card and it all went horribly wrong when the Greeks realised they couldn't pay for all those nice new SUVs they'd borrowed to buy.