I currently have an Oly OM1 50mm lens on my Alain35 but it needs to go because when it focuses it does this zoom distortion.

So I need a new lens, What do you suggest?

By zoom distortion when focussing do you mean "breathing"? As if the camera zooms slightly any time you focus? If so, the way to fix it is to get an "internal focus" lens. Nikon's AF-S series is internal focus. Not sure about a similar Canon series name, but you can be sure that in both cases they are the most expensive lenses in the line up.

Thats exactly what I mean, Thanks Joel!