Re: to our 40% that will surely come
No, the UK will leave the WTO when it leaves the EU, unless the great powers force (EU/US/China) the WTO to ignore the rules. Considering that the WTO is absolutely crucial to world trade and especially important at a time when that trade is under scrutiny, I doubt that they are willing to do so.
Under the rules, the UK cannot trade with WTO members as it has no agreed quota (it trades under EU quota). So it has to leave the WTO until it negotiates an agreed quota schedule with every single WTO member. But while it is outside the WTO, no WTO member can make a trade deal with it that would give it better access than WTO members get. So while it at least gets to trade, it cannot actually make trade deals.