I guess you are buying traditional spraypaint for D.I.Y, wich in the u.k are painfully expensive and very basic colors.
Try to have a look in shops wich have some conection with hip hop music and fashion or other urban alternative culture shop. They should have grafitti art sprays wich are arround 3pounds and have way more colors than you will ever use.
where do you live? Monstercolors.com are from glasgow and its quite good spray. 2,49 a can.
Best luck
