Good Morning Mike
Mike, according to the information I received from employment experts, the crux of the matter relates to contract terms (are you really employed?), permanence (length of agreement) and bonding/training terms.
18 months ago a considerable amount of research was carried out for interested parties and the terms and conditions of 2 UK LC carriers and 1 holiday/charter airline were scrutinised.
I have to say that (according to EU employment-law experts) no breach of the (then) legislation could be identified.
As for taking action against one's airline-employer, IMHO that would be curious way of making one's self persona non grata in the profession!
Hope this helps, I had the great pleasure of being in this game in happier times for almost 25 years and feel greatly for young men and women now joining the party. Good luck to them all. bm