Re: claiming the tax back
"From a UK perspective, if a 50% tax payer gives £10m to their pet charity, they get a £5m tax rebate. That £5m would have gone to government spending - effectively taking £1m from the NHS!!!"
I don't believe the issue is as black and white as that - for short-to-medium term objectives and smaller scale requirements, charities often outperform government/public sector in delivering both value for money and successful outcomes. While the NHS may deliver the best value for long term, national projects they aren't perfect.
While £5m donated to an animal charity (as an example where the money doesn't directly benefit people but may still benefit the wider community) may mean money is taken from the NHS, £5m donated to health, education, welfare and other aid charities does not automatically mean a loss to the tax payer.
Which leads onto the larger question of charity - can individuals make beneficial decisions around how money they have earned should be spent to the benefit of the wider community or do you leave everything to the wisdom of central/local government and the public sector?