I work in the City and a higher rate taxpayer (both here and in the USA, the joys of an American passport - double taxation!). Although I am a fabled "non-dom", because I receive a salary I pay more than 50% of my income in tax as well as paying tax when I transfer shares, etc. I have the money to pay for that and don't resent paying into the system when I don't take advantage of almost any of the services - although I have private health insurance, just for the NHS alone I am happy to pay the amount I pay, particularly when I compare it to the frankly cruel situation that is in place in the USA regarding healthcare. I have made my home here and have an interest and a duty to make sure that other people are taken care of here on my doorstep, through a redistributive progressive tax system. (That sounds smug and halo-polishing I know, but don't know how else to put it.)
Just a comment on the richest 1% not finding it too disruptive to leave the country from a tax POV - that may be true for some but not for most higher rate taxpayers from a practical POV. I've lived and worked on three continents now and London has some major advantages from a business perspective - a strong and predictable legal system, a financial system that while messed up is nowhere near as messed up as elsewhere, and - and this is going to sound silly, but it's really true - the time zone. We coordinate all deals from our London office because we can deal with Asia Pacific in the morning, the US in the afternoon and Europe and the Middle East all day, so where do people want to live and work - London, so they don't have to take conference calls at midnight or 5am. And for people who are living here with their families, London offers a great lifestyle and excellent schools for those who have the means to pay for it. I grew up in Asia and I and many of my friends were sent to the UK to be educated - my family moved here for my brother and me to go to secondary school in London despite having no connection whatsoever to this country.
Whenever I hear people on the radio saying that all the richest people are going to leave London for somewhere else, I think to myself - where?? Continental European financial centres are in a similar time zone, but more expensive for the richest people as far as tax is concerned and with other disadvantages (just one case in point - my French colleagues have to fly to London first to connect to most places in Asia and sub-Saharan Africa). New York might be an option but the tax burden can be higher depending on where you live, is too far behind time-zone wise to deal easily with Asia and the US is not as international in its business and investment outlook (and their legal system is not the preferred medium with which to do business in places like the Middle East or Asia). AsiaPac has the converse problem - in fact the most recently elected chairman of HSBC tried to move his headquarters either to HK or Shanghai (can't remember which) and shortly afterwards returned to London because he couldn't run a global business as effectively from there.
Anyway, apologies OP, I have gone off the topic of this thread - there may be some very rich people who are sensitive to the tax rate and mobile enough to leave - but from my financial/legal/City perspective, there are a lot of higher rate taxpayers that no matter how much you tax them aren't going anywhere, no matter how international their outlook.