You will find that air the smaller airports the jobs that are available with the airlines are things like ticket agents and customer service type roles.
The interesting jobs, like dispatch and operations will be carried out by handling agents.
At the larger airports in the UK,LHR and LGW, and to a lesser extent MAN, you will have a far better chance of getting a job with an airline.
I dont imagine you would get a voluntary position with a handling agent. Its also entirely the wrong time of year to be trying to get a job in the industry in the UK.
Best advice would be to apply to the handling agents at the start of 2013 and see where it goes from there.