I'm not a millionaire, neither am I defending the super rich, but bear in mind that the top 1% of earners in this country pay 30% of income tax, and that figure has been rising in recent years.
UK Budget 2012: Top 1% of earners contribute almost a third of all the income tax | This is Money
Indeed, many of the lowest earners in society aren't net contributors to the system at all, as they get more back in benefits than they pay in taxes. Indeed, it is largely the "rich" who actually pay their taxes that are keeping this country afloat.
As for "taxing the rich until the pips squeak", well you're in danger of killing the golden goose, as seen by the many wealthy French currently living in London, and spending their money in UK rather than France, due to high tax rates in France.
Lets take the case of a millionaire living in a large house in Surrey. We can argue whether or not he is paying a "fair" amount of tax. However, what happens if tax rates rise enough for him to decide to leave? Does he clean his own house, tend his own garden, even do his own laundry? No, he helps employ at least 4 or 5 others, who will lose that work if he leaves.
Getting the balance right is tricky.
There's some sort of economic rule about taxes, how you can increase them and increase them, and more revenue comes in, but a tipping point is eventually reached, where further increase in tax actually generates less income, because the tax rate is now punitive enough to make it worth avoiding, but whatever method, including leaving the country if necessary!!