The covering of a paint does not depend on the chemical composition of it's solvent -organic or inorganic- but on it's content and "flux" of pigments. Any painter can explain this. Dulux has a good water based paint sold on trays with a high pigment content. The pigments are usually the more expensive part of the mixture.So they have cheated by diluting.
The old Irish cottages had been "white washed" with water based - well,ahem -paint.This forgotten technic is effective, saving a lot of money esp. in areas where there is no need for a weather proof coverage.Unless one wants to repeat it every year or two.
Check B&Q for their emulsions and buy some pigments of the desired colour to add.
Or,if going for the upper price class check Auro or Biofa, they do excellent covering water based paints. The Germans have a colour testing regime , to which every paint sold in Germany-beeing for professional or private use makes no difference- has to adhere to. Dulux has bought some well selling brand names there to get into the market, competing the existent market with their own brands would have propably been to difficult (expensive).
Professionals have to wear gas masks with carbon filters if working with organic solvant based paints under certain circumstances. For example in winter in closed rooms. This would make most paints based on organic solvents useless for about half the year.Thanks to our H+S inspectors work this is still not adhered to here. On the continent professionals use water based paints since they have the H+S laws.To be competitive.
So nothing to be afraid of, just buy proofen quality.