the truth is most of you southerners will be WORSE OFF than us northerners even if you hit £300-£400 a day due to crazy house prices and the general ridiculously high prices of everything.
my middle brother lives in surrey and his house cost £370,000!! 
....and its an end terraced house and that was a few years ago!it ll probably cost more now!my brother says its £10 for a burger down there and £8 for a pint of lager/beer! 
he was also paying £1800 a month rent for years and years when he lived in wimbledon(mines £308 a month).so over the course of a year he was paying nearly £18,000 more than me!!over 5 years thats nearly £90,000!!!SERIOUS MONEY! .
the best way to carve out a comfortable living in window cleaning as a sole trader is to focus your work in very affluent areas with good prices and live in the cheaper areas 15-20 min drive away with much lower living costs. 
House prices and rent certainly yes, everything else not really (perhaps service industry as well like window cleaning, gardening etc)
Tesco's etc same price wherever you are
Petrol about the same again
If i order something off the internet it's the same price wherever you live.
Ive just bought a brand new van it cost the same here in Essex as it would of done living in the deepest North.
Beer is not £8 a pint down here (perhaps in central london in some snobby bar) around £3.50 in my local pubs.
£10 for a burger perhaps in a large burger chain restaurant (byon etc) in general no its not that amount.
The best thing to do is have a house at crazy prices here then sell it and retire up north
