Re: Aboyt effing time too
"even though working through a limited Companies was their idea, sole traders got too many deductible expenses, and the Corporation tax rate was higher in times past when they dreamt this up"
Not my recollection. Inland Revenue (as it was then) never wanted PSCs. Why would they when they meant (a) more work: instead of one tax return they had to deal with a CT return, a Director's return and a PAYE scheme; (b) less yield: eg they allowed contractors to pay even less NICs - and NICS more than tax was often the big driver.. As for rates, during the 1990s the basic rate of income tax fell from 25 to 23%. The small companies CT rate from 25 to 20%. But comparisons had to allow for personal allowances etc. The CT changes that stoked the fires came after IR35 - the 10% rate in 2000 and (bizarre) 0% starting rate in 2002.
The HoC library has a good reputation for impartiality on such things so I commend their https://researchbriefings.parliament.uk/ResearchBriefing/Summary/SN05976.
Oh, and Inland Revenue staff advising Ministers had no reason to be jealous of contractors when they mostly had much more contact with (and more in common with in terms of background and skills) senior accountants, lawyers, bankers etc whose salaries and benefits dwarfed most contractors.