Distortion in Zoom Lenses

Just a quick post. I have always used prime lenses in the past fifteen years and only bought a zoom lens a year ago. One thing you need to look at before buying a zoom lens is distortion. I can not believe how much distortion there is in a £600 - £700 lens. I have found the Canon 70-200 f4 IS lens has very little distortion at 100mm - 180mm andso I use this lens for all portrait and engagement shoots. My Canon 24-105 IS lens does suffer from distortion at the 24mm-35mm end of the zoom range but is O.K at about 85mm. I use this for close portraits hand held indoors at 1600 ISO. So go out and get your zoom lens and photograph a brick wall. You will see what I mean by distortion.