A first diploma is good for people who have messed up their G.C.S.E's and thus may not have enough knowledge to gain entry into one of the apprentice possitions at an airline, or gain entry to the National Diploma or Certificates.
First diploma is a GCSE type qualification.
National Diploma is A level type (worth 3) and Certificate (Worth 2)
To get into University for a Foundation or First Degree you'll need to have at least National Certificate or A'levels or Level 3 like IB, Highers, BTEC, Etc.
This course will do no harm if you want to be an Engineer, it gives you some great foundations and will prove this is what you want to do to companies.
My Brother has done this course, and it seems that Apprentice Schemes with airlines still favour National Diploma from what i can see, and do think highly of people who have qualifications such as First Diplomas.
I know this as fact, people who got into a scheme from my brothers interviews either had First Diploma or National Diplomas/Certificates and even a FD. No school leavers with GCSE's was taken, showing that entry expectations are higher than the minimum standards.
Despite what above says, you need the qualification above this to get into Uni for Degrees or FD's.
Some colleges also run this course with practical experience so that an A licence is issued.
My brothers course is offering A licence with hands on next year.
An A licence will get you a foot in the door if you dont get into an apprentice scheme, it will also serve good if you do get on one.