When I was contracting I wouldn't get out of bed for less than £100 an hour, on a 4 hour minimum callout basis. This was plumbing and boiler maintenance mind, none of this PC lark. I got fed up with it rather quickly though and although I now earn quite a bit less, my quality of life has increased tenfold.
(this always irritates me with those contractors who go "I make £1000 a day", it's so easy to blurt out these numbers but what most folks don't realise is how much work is involved to get that job in the first place, and it'll only be for a few days at a time, you never know when the work is gonna dry up, you could be travelling all over the country, you need to juggle a million things at once, deal with crap customers phoning you up a month later going "it;s borked come fix pls" only to find that they hired some cheapo crap guy to do the work and screwed it all up, etc. Yes you can make that kind of money contracting but you'll have no life in most situations)