No one would dispute that in both cases the UK price is higher, but concern over the post tax difference should be directed to the Government and not Apple. A 30% differential is not that large considering the other costs of doing business in the UK and off course hedging against currency fluctuations.
The tax difference is outside of Apple's control, of course. But (strictly speaking) not the entire "post tax difference", as this also still includes a pre-tax price difference along with tax on that difference
Anyway, I was really only posting in expanded support of your calculation and in response to @motulist , to clarify how much of the US vs UK price variation is attributable to differences in taxation rates.