ag,you missed your calling. You really should have been a comedian. Yes, there will be economic pain in the UK, but the idea that they'll be desperate to join the EE (European Empire) as a result is ludicrous. If nothing else, it'll be easier for any excess labor to come to the US than the EE and I doubt we'll be any tougher on illegal English immigrants than we have been on illegal Irish immigrants in the past.
The real barrier to any deal is that it would probably require the UK to liberalize its pharmaceutical pricing regime, which would vastly increase the costs of the NHS.
