A lot of charter airlines in northern Europe hire their cabin-crews on seasonal contracts whereby you do not fly all year round. For these charter airlines the busy summer season is the last week of March until the last week of October. I'm not sure if it's the same with airlines across Europe, but know this to be true of English, Dutch & German holiday airlines.
It's probably worth checking on the websites of these airlines around January time when these airlines begin to recruit or look for potential hosties for their training courses. Do take in mind that airlines typically have a four-week intensive training course & that you may be working long & unsociable shifts which do not always match with college hours and sometimes a social life goes out the window!
Otherwise, scheduled airlines with their year round operations do not tend to hire for crews for only a particular time of the year.
The only charter airline I know that is hiring now is Air Scandic. They're recruting for crews for STN, NCL & EMA and I know from speaking to their crew members and their handling agent at EMA that they're not particularly fussy about who they're hiring as long as they're 18 and can start as soon as. Apparently the course is just nine days!