We live in uncertain times.

(I loathe uncertainty.)
That government report listed three scenarios, and I'm thinking the "Armageddon" variation is probably unlikely. So I am thinking it'll be somewhere between the first two options. Possibly toward the milder one for some aspects, and into the more unfavorable for other aspects. (At least, I hope so! It most definitely is not going to be business-as-usual.)
My guess is that there will be a turbulent period, possibly with occasional severe shortages of some items as supply chains sort themselves out. Consumer prices will go up, especially for food imported from outside the UK, I think. Unless the government steps in and puts caps on price rises (ala Jimmy Carter in the USA during stagflation in the 1970s) prices may spike badly to whatever the market will bear. Whether or not they stay higher will depend on what kind of deals can be made to get them back into the country at previous prices. That will take a bit of time to negotiate, and the prices may or may not go back to current levels.
I've seen some reports that even now UK farmers are having a tough time finding people to harvest their crops, as workers from Eastern Europe who formerly were eager to come here to do that kind of hard, manual labor are no longer lining up to do so. Since local talent doesn't seem interested in filling the labor gap, there will most likely be a knock-on effect as farmers lose crops, and subsequently don't plant as much in future seasons. Unless the government creates some sort of incentive program to bring that labor pool back. And those unfortunate farmers who can't take the financial hit of the lost crops go out of business. So, some foods traditionally available from UK sources may no longer be available in the quantities usually seen, and with shortages one usually sees prices rise.
Energy prices - how dependent on outside fuel is the UK? Has the North Sea oil/gas field petered out, or can it be run back up to a higher production level? I am assuming that even if not, fuel doesn't come in primarily from the EU, but from elsewhere, so that shouldn't be a horrible issue - unless
refined fuel comes from the EU? If so, again, a period of turbulence, possible shortages, and it will even itself out. Unless favorable trade arrangements are made, prices may be painful.
What the pound will do? I doubt it will go up. How far it tanks is open to conjecture. At one point I had thought I might move a lot of my savings into pounds. I believe I'm going to leave them sitting as dollars, instead. I'm not wealthy, so I can't take a 'hit' on the exchange rate if pounds do falter and we need to relocate elsewhere. (I am hoping we can stay, but that will depend on the UK government and living conditions. I can put up with a lot of inconveniences, as far as daily living, but if taxes start to skyrocket to prop things up, my budget won't allow us to stay.)
It makes sense for companies that can relocate for their advantage to move out of the UK to an EU country, if the bottom line is that it is more profitable for them to do so. And for entities outside both the UK and the EU to not locate inside the UK if the majority of their business is in the EU. (Bank of America has just decided on Dublin for their new, big, European hub site.)
It's really a shame to see the EU in the current state - it was such a grand experiment and seemed to be working relatively well (as far as these things do). I would hate to see it implode, because in that scenario there will be a lot of people who will end up suffering a lot greater hardships than they're dealing with now.
I have only been here a year, but I've done quite a lot of "people watching" in the aggregate. Based on what I've seen at the grocery stores (panic, hoarding, etc.) from a three-day snow event, I am kind of wincing in advance over what people who have been used to having what they want when they want it are going to be like immediately post-Brexit. And all the finger-pointing that's going to go on.
But, in the long run, as after WWII, things will stabilize and life will go on. Into what sort of conditions it all resolves to remains to be seen.
But it's not the end of the world, regardless.