It is a cost of the employment. As I wrote above, it goes to the treasury and proportionate to the salary. It doesn't matter how we label it. Doesn't matter neither to the company's, nor the individual's taxation.
> Of course plenty of people earning big bucks don't do it via PAYE, just take their money as far lower capital gains
No, the people who earn big bucks do it in a non tax-resident way. They don't declare tax in the UK or any high-taxpaying region.
> That would only affect the top 2.5% of income tax payers
No, 1.6M people, the top 5%: https://www.ifs.org.uk/election/2019/article/labour-s-propos...
"The top 5% of income tax payers contribute half of all income tax revenues today." With the current level of digitalisation, there is only so much weight you can put on the most performant segment of the workforce before they pack and leave.
> Their tax rate would change from 45% to 46%, hardly an earth shattering change.
No, the former 45% would be higher than 50%, because it would have started from £125K, and they would introduce a 45% above £80K.