It’s great to hear from eager potential installers. There will be many people like yourself needed to transform our economy over the next decade.
The MCS-accreditation is the qualification required by the installation company only. This standards-based accreditation ensures systems are signed off legally, to a BRE (building regulations Executive) standard, and more recently, customers get treated with respect.
All you need to do is prove your competency and qualifications with any future employer.