This is an interesting read in the Guardian citing ex-Foreign Office chief. Sir Simon Fraser says short-term deal will be necessary even if Brexit is negotiated within two years of triggering article 50,
For me the critical part was:
His assumption was that the government would negotiate “some sort of continuation of our current access to the single market, rather than the negotiation of a completely new agreement and arrangement.”
This would mean that the posturing towards the right-wing and hard immigration controls would be conceded after a couple of years of financial pressure. So perhaps not such a Hard-Brexit?