I have just found an article in the Speccie that covers this issue.
It reminds us that Gordon Brown, the man who introduced the 50p rate did so as no more than a trap for the Conservatives using some massaged figures. It also makes clear that, his trap aside, Brown actually agrees with the points I made about the impact of his 50p rate and indeed even a 45p rate.
This sums up Brown - all he cared about was stuffing the Conservatives even if his policies, as they have, cause massive economic problems and job losses.
Here is the link to the Speccie article:
http://www.spectator.co.uk/coffeehouse/7145773/brown-still-hovers-over-the-50p-tax-debate.thtml
An extract here:
"""""""""""""A number of papers report today that George Osborne is minded to replace the 50p tax with Gordon Brown's original proposal: a 45p tax. How the ex-PM will be laughing. As he knows, even the 45p tax will lose money — that's why Labour didn't raise the top rate until the final four weeks of its 13 years. But the Tories haven't worked that out yet, and the Treasury is still working on the false assumptions he programmed into it.
In short, the amount of money that either tax rate will raise depends on what's called the "taxable income elasticity," or TIE — a figure suggesting how responsive various taxpayers are to rate changes. It varies for income groups. The lower-paid are less able to move their labour or money around than the rich. As various countries across the world realised this, they worked out that the best way to squeeze the rich was by lowering their tax rate.""""""""""""""""
There is a graph that shows how countries have reduced top rates of tax to increase their tax revenues.