£400 a day??? - I wish.
Best rate I ever had as a contractor for desktop support\project rollout was £19ph back in 2001, closely followed by £17.50 - 18.50 around 2004-2006.
One of the lowest rates was working for a local authority that paid £12ph, it was a substantial rate cut I took from the 2006 rate, just to be closer to home for the wife & kids.
The very worst rate of all I took when there was absolutely nothing to be had was £78 a day & I took that because it was based in my city centre about 20 mins walk away from my house.
As others have stated the rate you take is not the rate you pay yourself, its there to pay the tax's & both sets of NIC's, to pay accountants, to pay yourself between contracts\sick pay & holiday (actual family holidays not ones enforced on you by sudden contract terminations). I earned far less overall than the permies taking all that into account with far less job security & I was far happier than most of the permies when I was working & I wouldn't have swapped that experience for the world.
After being shown the door from the local authority along with some others, I managed about 2 weeks backfill work & 3 interviews in four months before I gave up my Ltd co & utilised my (new) residency status to move to Canada.
Coat because you need a good one here.