Two things to add:
- A £500 daily rate is very attainable when you work as a contractor in London. a £105k salary for the same type of work - not so much... I would argue that most people don't really have a choice and they HAVE to become contractors to get that kind of money.
- Nobody is forcing you to take ALL the money on your company account and pay it to yourself as a dividend. You can leave most of it there, or even invest it on the company's behalf. You have the power to decide when you want to pay the taxes on this money, and this can be very valuable. And there are other (perfectly legal) practices that can keep you in the lower tax bracket. If your accountant did not explain these to you then it's probably time to look for a better one :)