Menzies (KISS) have all of their recruitment done through an external recruitment agency called Aviation Resource who you'd have to get in contact with, unfortunately I don't have their details to hand right now. This summer has been busy for Menzies as it's been the first they've handled an airline other than bmibaby & Eastern.
I don't see any handling agent positions either on the ramp or on the passenger side opening up until February/March time which would be the best time to contact. In the meantime, try Coventry, friend recently tried out for Aviation Handling, and they're meant to be a fine little company.