Not necessarily Gromit, they "park it" outside the UK - there's something that folk seem find hard to grasp in terms of salaries, bonuses, commodity prices etc etc is that we live in an increasingly international market and the money gravitates to the sinks offering the highest return - and that this is really hard to legislate against tax-wise.
Is it ethical, perhaps no, but then it isn't legal until proven. This is not just at the income tax level....let me give you one example - I had one major UK Conservative minister doing his nut (and ambassador) when asked where we (Intl Co) where placing our investments out of - Answer then the Netherlands and not the UK - why "because of the preferential treatment given to tax rollover of losses incurred in Years 1 to 5, the Dutch being far more favourable."
I finished off "Go upstairs and see Unilever and you will also have the same answer."
The answer isn't about 40% or 50% at the high end though - its about encouraging new industries and investment by driving favourable tax deals to encourage them to open up here and take employment, esp outside the SE.