Ian,
INCOME
Get a 2006 Day to a page A5 Diary.
Each day you work, note the houses you cleaned and the amounts and who paid you.
Add up the amounts and write that at the top of the page.
(This method can also assists you in keeping track of who you have cleaned, when they're due again and who owes you money.)
That's your income aka turn-over.
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EXPENDITURE
Get an A4 ring binder.
For any item you pay for, for the maintenance of your business, keep the receipt.
If it's not A4 already, staple it to an A4 sheet of paper and put it into the ring-binder in date order.
Keep a running total of what your spending.
This bit's a little more complex, but if you use some common-sense, you won't go too far wrong.
That's your expenditure.
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So income minus expenditure = profit, and it's the profit you pay taxes on after you've used your personal allowance.
If you still really haven't got a clue, you should phone the self-employed part of the tax office and ask for courses and dates. They're run regularly and in many different locations.
I believe they last just one day and should tell you everything you need to know.