I quite like this site for facts and figures:
https://oec.world/en/profile/country/deu/
The point with tariffs, which imo is not the biggest problem, is that you lose a degree of control where for the most part you have to have the same tariffs for everyone and your tariff schedule and quotas has to be agreed by other members of the WTO and of course it's the importer and subsequently the consumer who pays the tariffs. If you reduce tariffs to zero or low for everyone the market is going to be flooded with imports and UK manufacturing will suffer.
You also have to have the infrastructure
Being protectionist is true but you can't be more protectionist than Trump who will do anything to protect the USA, unfortunately he's making a right mess of it and starting a trade war which will lead to economic downturns for all,whereas UK seem to want to be like Trump.
The biggest problem will be the supply chain and whether the UK like it or not , it is an island next to the European mainland and relies on close co-operation with its neighbours and speed of supply. Also the speed of documentation and have the personnel and infrastructure in place to cope with the massive increase in documentation and checks which will be required. Also bearing in mind that even if the UK wave everything through unchecked the EU won't do so going back the other way.
Additionally most of the traffic with the continent, lorries , drivers etc are nearly all European plus the number of licences that will be able granted to UK businesses traveling to the continent will be severely limited.
Really don't see how the UK copes with all these problems if and when they become a "third country".