Mc Aero,
I can't think of a specific material benefit of C ENG registration, other than if you were looking at a new job and promotion then it may tip the balance in your favour, however, it is a highly regarded qualification in the industry, and is a personal achievement, plus is recognised overseas.
Certainly have a look, and if I can help get in touch.
Clarify the fees,
Annual subscription is,
Membership of RAeS as Member is £177.00
EC (UK) C Eng fees is £26.00
Gross amount £203.00
Best regards,
om15