Public spending as a percentage of GDP would obviously fall sharply, and those that depend on public spending would certainly feel the squeeze (although social welfare recipients could be given the option of staying on benefit if they relocated outside the City). But against that, Hull would attract entrepreneurs and private investment on an unprecedented scale - and with its easy European access, much of the inflow would come from overseas. There would soon be jobs for all.
I've had to turn down several job offers from several Hull-based companies as the returns quickly diminished when I factored in the cost of travel and tax making my take-home wage significantly lower than minimum wage; but significantly reduced taxation? That alters things quite a bit.
A future consideration for LPUK policy? I don't want to live off the back of you shandy drinking southerners- I want to compete and reclaim the revolution the collectivists have eroded over the last 3 centuries.