Done both contract and perm over the last 12 years
I went contracting at the start of 2008 as I had moved several hundred miles cross country with work only to be told my job was at risk and then the housing market crashed. The main reason for doing so is that I could take rent out of pre-tax income which then meant to say I could afford my mortgage as well.
In 2010 I tried to contract in Brussels, the agent effectively said "trust me I'm an international tax lawyer" when I was querying about limited company contracting. It turns out that the fine I was up for would be more than 100% of income. Apparently all his colleagues used umbrella companies based out there. Also, as a British national, I had to fill out a Limosa a.k.a. a work permit application.
This year I found out that France also does work permits - there is a minimum income which varies with number and age of dependants - as some remoaning sponger wrote to the newspaper saying that they were being kicked out "because of Brexit" as they had applied to be naturalised and the French replied that they shouldn't be in the country in the first place.
One thing to note is that with a level playing field between public and private sector contracting the exodus that happened in the former will be addressed so you can see why they are doing it.
I'd be happier paying tax if the sponging royal family didn't have all those tax breaks.