Re: Two things
"no paid holidays, no sick leave, no safety net"
Contractors do get a safety net with all those benefits. In fact the benefits can be unlimited. They just need to speak to the owner of the company (themselves) to ask what benefits they can get. How are these benefits paid for? Well by the fact that contractors earn significantly more than the permanent employees. For instance in some areas of the country an employed web dev will get say £50k. However a contractor will be on at least, pro-rata, £104k. Previously the take home would be more due to dividends and NI lowering tax compared to PAYE.
Even if the tax liabilities are adjusted based on IR35 and some of the conditions also then the day rate will remain the same and therefore there should be sufficient extra income compared to permanent that will cover Sickness Insurance, holiday periods, between contracts etc.