lifeinchrimbo You said that the poor spend on necessities that they lack, - I don't doubt it. But what on earth does 'if it is truly necessary the rich will already have it' mean, exactly? 
Things that are true necessities are food, (and the means to cook it) heating and hot water, a bed, basic furniture, basic functional clothing, access to healthcare and education, and these days access to (and ideally ownership of) a computer for internet access, a basic phone (either landline or mobile) and access to some form of transport. Then there are a handful of other less important miscellanous things, that make life much much easier but are not, strictly speaking, essential - like TV, hairdressers, etc.
Of course the rich have all those things -a and so, to some degree or other, do most of the poor, apart from the homeless poor. If you are saying give a poor person money to buy a washing machine and it will boost the economy, and save them money on launderette costs - yes, I won't argue with you there. But the rich person has to buy their own washing machine as well - it doesn't magically appear in the utility room without money changing hands.
The only reason they already have those things is because they buy them!
And tell me again how education would be improved by the rich adandoning private education? I never quite get that one. Are you suggesting that they transfer that their £20k a year (or whatever they pay) as an extra enforced tax that goes straight into the education pot, beacuse if not, I fail to see what difference it would make.
As far as I can see, the only difference would be that the educationally/socially elite would become slightly less elite, and league table chasm would become even wider than it is now, between schools in very expensive middle class areas and those poor areas with 'failing' schools.