There is a whole thesis to be written on the subject, I will be really blunt when I say there is a reason I pay and have always paid a trusted accountant and followed her advice to the letter (including having a single bank account).
Tax is complecated, now why this is depends on your opinion. Some will suggest it's meaningfully complex to try to trap people. IMHO I think the reality is it's a nightmarish mess created by generations of self serving politicians and civil servants layering further regulation and rules on a system without amending, fixing or dissolving obsolete parts. I think we are also at a part where if we stripped back the system and charged it fairly per person/buisness on income annually you'd see a uprising. People DO NOT realise what they are actually charged on there earnings, repeatedly.
Theres a massive conversation to be had on taxation, fairness and benifits. I was told day one that being self employed is as much about having a buisness that suits what you want as much as what earns money..... It's compleltely correct and there would be zero point doing it if I did'nt enjoy it and live for it. I think that is where those running Ltd often wind up missing the point with there intrest becoming purely financial over the quality of life it gives them.
Benifits needs reform, I think the most intresting concept of our time is a universal basic income paid by goverment... Remove all other benifits, just a financial payment that is enough to cover the rental of a modest property, food and energy. Now on paper I hate it, I have never claimed any personal benifits in my life or welfare..... In reality I am in a minority, with the vast majority claiming something..... Just cut the crap, put everyone on a level footing and get on with it. Should a multimillionare get £1500 a month for example? No, But then if any additional personal income over say £15000 a year is taxed at 40% it suddenly becomes fairer and viable? That £1500 gives a majority the backing to either do more or less? But studies are increasingly showing it means they have the confidence to go, do and spend...... all drivers of the economy.
In terms of works vehicles alone, IMHO we need a massive reform on vehicle tax, licensing and insurance...... All three should be charged on an individual basis for private/sole trader use.... I.e you as a person pay the Gov X per year to cover you to drive any vehicle on your license for road tax and insurance. Any companies pay a tax rate per employee who drives.
Just my thoughts.