There's a very good article here about why wealth taxes don't work:
https://www.taxresearch.org.uk/Blog/2024/05/10/wealth-taxes-wont-work/
The TLDR is that they don't work because it's going to be almost impossible to untangle the assets of the very wealthy to work out what their wealth is in order to tax it. Instead you tax on income and capital gains when that wealth is used in the UK. You close the offshore and non-dom loopholes so everyone pays a fair amount of tax. You could even get rid of the arbitrary tax banding jumps in favour of something much more progressive.
Another idea which works for me is that once an individual has a net worth of say £50 million, the government gives them a gong saying "you've won!" and any additional wealth that is generated is used for the benefit of the country. Maybe you could consult about what the wealth should go toward " we need a new hospital Lord Ashcroft - how does the Lord Ashcroft Memorial Hospital sound to you?". IIRC it's what the wealthy used to do - build schools, hospitals etc to show how generous they were.