I agree with CavortingCheetah in as much as the proposals at the moment are very wide reaching and will affect many unsuspecting people.
For instance,as far as being in transit passing through a port, where does it say you are not liable for UK income tax? What about transiting between LHR and LGW? It seems to be a sledghammer to crack the non-domiciles nut. However, the IR document does also refer to the non-residents that "escape" UK tax. But then again, if you are resident abroad, why should you be liable for UK tax?
I have no doubt that this is going to cause a lot of grief through the law of unintended consequences.