Re: £550 million, eh?
I returned to a public sector engagement (not one of the two you mentioned), in which the organisation has deemed that all contracts are within IR35. I told them it would take a 40% increase in rate (from the previous non-IR35 engagement) to make it worthwhile, expecting them to decline. They did not.
So... HM Gov dept pays me 40% extra, then another Gov dept reclaims this in tax and brags about how much money they have 'made'. Durrr...
I can see the private sector simply doing what we all hoped they would years ago, and tailoring contracts and working arrangements to be firmly outside IR35, as I can't see them rolling over and paying 40% extra so easily.