"businesses that benefit from EU contracts and monies should relocate to an EU27 member state PDQ"
I doubt they actually needed a government warning for that.
The big question is how far does that reach? Any business that was established here by a foreign investor because the wanted a plant or office in the EU must clearly be at risk. Such investors might not yet have would up the UK business but you can bet (in fact, the leavers have already bet on our behalf) that they'll be looking at alternatives for future investment.