Upvc euro cylinder lock?

Hi , this has got me round the bend , I have getting a used upvc front door and bought a new cylinder lock so I removed old lock (1 screw-easy) but when I fitted new lock the handle won't lift up to engage the hooks ,? So when I remove lock and look were screw goes to fix lock in place there is a brass slider bar that slides up and down as handle is lifted, so when screw is in that's what's stopping handle lifting!? now I'm a builder and can overcome most problems but this has got me beat !lol , so if anyone can help would be great, thanks