I'm old enough to remember the 70s when the likes of Keith Moon, Shirley Bassey, Michael Cane, the Rolling Stones and many others all left the UK. Driving our talent abroad won't help anyone except the countries they move to.
The Duke of Westminster paid no inheritance tax (but does pay income tax). The lack of IHT was because the estate isn't his, He can't sell, it is held in trust.
Perhaps you want to target trusts specifically. The govt could act to limit the use of trusts if it chooses to.