I don't get out of bed for less than £500 a day. I wish!
In 2009 I earned about £33k before tax which averaged around £2750 per month pre tax, however last year 2010 I only earned £26k which is £2166 per month pre tax and for that I spent around £7k on tools, consumables, advertising, training course, memberships, certificates making my real wage £19k for the year pre tax. Not sure how much I spend in 2009 but I imaging it was around the £10k mark but don't have my records that far back on computer.
For my sums, to make £1800 per month pre tax you only need to be on £11.25 per hour which is well below what you can charge for yourself, the hardest part is getting 40 hours per week.
To keep busy over the last couple of years I have branched out and now do data, alarms, cctv, aerials, satellite and home automation as well as general electrical work. Some may say a 'Jack of all trades' but most of the work I now get can include a bit of each without compromising on my quality.
I assume by being so specific on the amount needed per month, you have worked out your outgoings and living expenses and £1800 is what you are looking at spending per month to sustain a quality lifestyle? Keep in mind that domestic work is never guaranteed to be the same every month and some months you find it harder to earn.