Regardless of the over running and additional costs, although the quote does suspiciously look like he’s trying to claw back the over run costs.
I just had a look on Screwfix. Cheapest wall paint, £16 for 10ltrs. Should cover two coats, but if it’s fresh block work, 3 of 4 coats. Floor paint is £35 for 5ltrs. Again should cover in 2 coats. At best that’s £51 for paint, no tools.
It’s 1.5 days work minimum. You can’t paint the walls once the floor is down, etc.
How much is anyone here prepared to work for? Minimum wage? £10 / hour? Got to pay your tax remember. £15? Oh, you need to run a van. £20? We’re getting there. Also time to fetch the paint, clean up. 2 days work at £25 / hour.
Cheap materials, tools, and 2 days, very cheap labour. £600 + VAT?
So £1000 for someone tidy using good materials?
DIY.