Hello
If you use the search engine on here, this question has been asked many times (regarding different diploma companies I must add). The answer usually given is a "no" as most airlines like to train you to their own standard.
Personally I would save the £75 and put it towards a decent suit for any interviews that you might be lucky enough to get.
Working for easyJet, a diploma would be pointless. You go through a selection process during an assessment day (they look at your personality, ability to operate as part of a team, how you cope with stress when performing a timed activity etc), the diploma won't help with that. You then have a formal interview (if you pass the assessment stage) and a diploma won't help with that as they will be asking you questions about yourself personally and how you have performed in certain situations before.
And, when you commence training, the airline will train you to it's own standard, will provide you with location of SEP equipment, formal training on equipment, first aid and lot's more.
So, save your money and just get applying to different airlines and good luck to you
