Typically speaking you nailed it on the head, these jobs ARE in fact few and far between. Most of the staff that you see in the respective airlines uniforms are in fact handling agent staff in the airlines unis (Virgin, PIA, Etihad, Emirates etc etc...). I know that these airlines also do employ their own staff but these tend to be only in supervisory / management type roles and then it is a case of not what you know but whom....
If you wanted to work directly for an airline on the ground, SAS and bmi are about your only hope at Manchester (AA havent hired in dog's years!). A bit of a word of warning though... SAS handling is on shaky ground at best and whilst the concessions are reasonably ok, the pay is horrendous (bordering on insulting) at bmi. What good are concessions if you cant actually afford to go anywhere?
My suggestion would be to try handling agents as they are the easiest to get into (on the pax service side at least) and there is more potential for career progression. I work for a handling agent, having previously worked for an airline, and I love every minute of it with absolutely NO regrets
Hope that helps!