@Jengnr
The reason contractors are paid more isn't to cover their clients/employers' decisions to enforce random days off. It's because they have to pay their own holiday pay, sick pay, pension, tax and NI. They get paid the equivalent of what the employer actually pays to a full time staff member once all non-salary costs are included - so it looks like more, but it's actually not.
There are also contractors working in low paid jobs. My friend is a low paid worker in the media industry: she is a contractor on £18k even though she has (very long) set working hours, a desk and fixed responsibilities. (Her firm doesn't do full employment at her pay grade, because there are enough young people living at home in the city she works in who could afford to take her place if she left. So the employer gets away with it)
Assuming 235 working days a year, a day's pay for her is £76.59 before she's even put aside holiday pay, sick pay, pension, tax, etc. So her real-terms pay is about £60 a day which is under minimum wage for her hours and age.
Her employer recently announced a whole team compulsory Friday off because the boss was tired from a busy week. The boss presented it as a great and wonderfully kind idea just as you are here, @Jengnr. But my friend lost a full day of pay with just four days' notice. That is the difference between a nice month and a barely-scraping-by month. It adds insult to injury that she then struggles if she takes a day off when she pleases, because she doesn't earn enough for proper fucking holiday pay anyway.
My point is that it doesn't matter if the reason is a tired boss or the football. When contractors are involved it is different, and pointing it out isn't pissing on people's chips.
Yes while it is perfectly legal and everyone has consented to it, shutting up shop with a few days' notice is also a choice that employers like tiggyt and my friend's boss make. What I'm saying is that they should exercise that responsibility with caution. Yes I agree that if Tiggy's firm is in an industry where all the contractors are paid £50k then it's a bit different, but we don't know that - and it's still shit for the contractor, albeit less so.