Cooke and Lewis mixer kitchen tap. Help please!

Hi all, hoping for some assistance to make a frustrating day worth it. I have sought to replace our mixer taps cartridge today. The hot and cold is controlled by seperate levers . In order to replace the cartridge I've taken the levers off- difficulty is in getting them back on. There seems to be no obvious way of attaching them and I wanted to see whether anyone else here has had this problem.

I will see if I can put up a picture to assist but any preliminary suggestions would be very welcome.