They don't guarantee you a job, this quote is lifted straight from their FAQ
"
Am I guaranteed a job if I pass my exams?
We provide our candidates with complete career support. We will provide you with everything required to ensure you have the best support possible to achieve your dream career. Our Careers team will provide you with all the job search support they can. Rest assured, we have successfully helped thousands of students find leisure and tourism employment with some of the UK’s largest organisations. However, the ultimate decision as to whether or not you will be employed is with the employers."
I believe the general advice on this forum is to avoid like the plague any company that tries to charge you for flight attendant training. I don't think anyone here thinks it makes any difference to your chances
You are better off devoting a day to reading through all the recruitment threads here