I dont mean to be pedantic or picky, but IMO (and Im only saying my opinion, not wanting to start anything here)
But £20.00 an hour isnt enough. Of course it depends on your own personal circumstances (are you married, kids, single, mortgage, rent bla bla bla). But when you take into consideration travelling time between jobs, lets say you had 3 connies to do like that, with 15 mins travelling time in between each one. You'd earn £60.00 a day, not enough for a self employed person.
When you also take into consideration down time due to weather, down time due to sickness, down time due to holidays, down time due to bank holidays, running costs (vehicle, kit, materials, insurances) £20.00 an hour for the bare minimum you need to add on another £5.00 an hour and thats without earning anything astronomical or outrageous when everything is taken into consideration.
I think the trap a lot of guys fall into, and I did permanently for a few years, and can still kid myself with it sometimes, is that we can think 'Oh £20.00 an hour, with 40 working hours a week, I EARN £800!
Nothing like that is it.
JMO, no offence intended.
Matt