IMHO people don't need a report in order to work out the consequences. The fact is, the EU is our biggest export market and therefore it is logically inevitable that if our ability to sell into that market was impaired, it would be bad for our economy. At the very least in the short term whilst we took time to develop other markets. British companies selling into Europe would be significantly disadvantaged - and those who are teetering on the edge of bankruptcy already, would be forced into bankruptcy. I can't see how anyone could argue this is not the case.
So the whole debate really hinges on one central point: If we were to leave, would we be able to negotiate any time soon a trade agreement that gives us broadly the same access to the European market as we have today, without significant strings attached and penalties, tarifs etc. People should ask themselves that question.
For me, the answer is blindingly obvious that EU can never agree to what the Outers suggest we can have. If they did agree, more or less every country would want out. And they also couldn't agree because it would be damaging to individual countries' prospects. Their businesses, burdened with EU regulation and costs would be asked to compete on a level playing field with UK companies that are not burdened in the same way. The UK companies would do better in those circumstances, with less regulation and potentially lower cost base that their European counterparts. The European national governments recognise this and therefore will not agree. France has publicly stated it will not agree. Trading freely in the EU, necessarily requires participants to agree to the basic same rules on working conditions and movement of labour etc. It's not optional.
So this idea that we can leave and everything will be roses because we can enjoy all the benefits of openly trading with the EU, but none of the downsides, is honestly pure fantasy. It can never happen. It's obvious when you think about it.