I am slightly concerned that you claim to be a painter but..
a) don't know how to calculate how much paint you will need
b) don't know the difference between M2 and square metres
c) don't know how much you should be charging.
Hi CheekyChops, you seem to have the same worries about these posts as I do. I worked as a Painter and Decorator for a number of years and estimating paint and wallpaper quantities is not rocket science. Most of them even have a picture on these days to show you how to make the measurements.
I've just had a quote for �110 per day for labour, plus materials. I live in the West Country.
My son who lives in the West Midlands has had a quopte for doing hall and stairs at �140 per day, plus materials.
Hope this helps.