I would agree that the UK tax system is over complicated, and often unfair. Council tax, in particular, in that the nominal value of a house bears no relationship to current income and ability to pay. Now retired, I probably get about one third of what I would receive if I was still working - but my council tax bill is unchanged (i.e. a much higher percentage of my income). Yes - i know that "THEY" claim that property-based taxes are relatively easy to enforce - but that benefits the system, not the individual.
The VAT scheme involves much administrative work, with payments & refunds if, for example, you buy materials, process them, and sell finished items to someone else.
Now I know this will never happen, e.g. the likes of Daily Wail, Torygraph & Scum would try to convince people that it was "unpopular / unworkable, etc."
1. I would replace VAT by individual rates of sales tax for each class of items, the tax level being related to the effects on health and the environment. So, for example, tobacco, alcohol, sugary foods would have the highest sales tax rates - as would anything that created vast piles of waste that went to landfill, or was expensive to recycle.
2. I would abolish council tax.
3. Assuming that the government could ever make computer systems work.... - I would make income tax the main method of revenue collection, but with individual tax adjustments for everybody, wiith tax reductions for those doing socially beneficial jobs.
Income tax would include a local contribution to where you lived, and your tax band rate might be reduced, for example, by up to 10% if you were a nurse, doctor, waste disposal operative, etc., but not reduced if you were an investment banker, footballer, etc.
It would also be necessary to close tax avoidance methods, e.g. no money earned in UK could be sent overseas - until it was confirmed that all taxes had been paid. And heavy penalties for trying to use devices such as phoney "payments for services" to overseas companies.