Cogito-
Last time we made it too difficult to be wealthy in the UK with 90%+ tax rates, they relocated overseas.
Really? When would that be? Would that be during the 1970s, when income inequality was at its lowest, and people had a great deal more disposable income than they do now?
Professionals are already leaving the UK in higher numbers than in the past.
And what evidence do you have of this? Did you just make it up?
Seeing as this government is cutting corporate taxes, reducing funding for 'HMRC', and is ideologically bent of privatising all public services, I don't think the UK is any more 'business unfriendly' than it has been in the past (financial crisis and banks unwilling to lend excepting). In fact, the opposite is probably the case. Structurally, the government continues to seem to want to kiss the arses of big business and the rich at the expense of the public.
Making rich people poorer doesn't make poor people richer
Actually, it can do exactly that. All the money which is rewarded to the very top earners in the form of bonuses which are rewarded to them regardless of performance (and this practice is widespread), detracts from the corporate budget which could otherwise be spent on those at the bottom end of the payscale.
All the money which is collected from the millionaires in the form of taxes increases state revenue, which can be used to provide tax relief to those at the bottom of the pay scale.