I believe you can work unrestricted on a family / de facto visa, but as with any visa question it's better to get the answer from the authority that issues it... a forum isn't the best place to get advice on legal matters like work and visas.
It's also worth asking yourself if you'd stand a good chance of securing a job in the UK, demand for jobs is as high here as it is at home, and for every recruitment run in my airline we'll see hundreds of applications for maybe 20 or 30 jobs. Most of those that we take have worked for us before on a seasonal basis, although some are fresh from an unrelated line of work.
The ID and background checking requirements can also be a complication in a UK airline, it's difficult for us to do the paper trail for a candidate who hasn't always been resident in the UK, and time (the recruiting / start date window versus the time needed to get overseas work history and references, foreign police criminal record checks etc) can be against you.