Everyone seems to be missing the point of the EU
It prevents all the silly squabbles between the different EU nations from escalating. (Trade wars, hundred year wars, world wars, etc.)
It seems to me that there are only two likely outcomes of the two year exit negotiations. (To extend it beyond that requires unanimous agreement of all states, which would seem unlikely).
A complete exit with no agreements. This will result in the obvious tit for tat regulations and actions (perhaps the £35K rule for foreign workers which would then apply to EU workers, might be adopted by the EU for English/UK workers in the EU). Any EU country with an issue with us would be free to screw us over.
The other option is England becoming simply part of the EEA. This would mean business as usual, (except that we would not have to meet so many environmental and work related minimum standards) however this would be exactly what the kippers wrongly claim the EU is, so is hardly likely to be satisfactory to them.
Also has it occurred to no-one that after a brexit the EU might offer relocation grants/sweeteners for businesses that wished to remain within the EU (the obvious ones being data centres and multinational EU headquarters)?
Of course all relevant business decisions will wait until the result of the referendum. (I have already noticed that the contractor market has been a bit dry, with upgrades and expansion being put off, because it would be simpler to buy new kit in the new offices in the event of a brexit vote.)
If the result of the referendum is overall exit, but with Scotland being stronger remain than they were remain in the UK, then decisions might even be put off until after that had been sorted. (Easier to relocate to a different part of the UK that won't be leaving.)
Business will assume the worst possible result for the exit conditions and plan for that. The one thing they know is that the UK will remain within the EU for 2 years from the date of notices of withdrawal. (Which in my expectation will be 31st Dec this year, to allow time for a second Scottish referendum.)
2017 (and perhaps 2018) should be rich pickings for IT contractors (all those relocations) , however it would be very wise to invest any earnings carefully for the drought that will follow. I certainly wouldn't like to be poor in a post brexit England.