Hi shbee,
Getting work experience after GCSEs is definitely harder, as most large companies only hire interns at undergraduate level, and even those places are competetive. From an engineering perspective though, cars and planes are similar enough at a GCSE level, so if you wanted things to add to your CV reaching out to local garages to ask for internships or part time work might be an idea, this will also help with thinking through the problem solving required for aerospace whilst getting used to the materials and the structure of engines. From personal experience, aerospace or engineering companies such as BAE and Rolls Royce value this type of experience as it really helps later when taking designs and making them realistic in terms of materials and safety.
I also don't know if this is an opportunity for exposure near you but AirCadets could be of help with getting in touch with some plane companies,
best of luck!
Sophia - Lancaster University School of Engineering Ambasador