There are no necessary requirements per say, yet there are requirements for jobs in the industry that individuals must consider. Employers like to see your experience via projects you have worked on. For the industry, having a "reel" or portfolio of your work is fundamental. Having a University Degree or equivalent can also be beneficial, yet if you have an outstanding reel it can be just as effective. There are degrees that can offer good experience, such as Production, Sound Composition and Sound Technology. There are specific institutions around the UK that specialise in sound and music which can prove useful on your resume if the schools have reputation.
You can gain experience by working on student projects, (effective with University), conducting work experience or placements alongside current technicians,assisting in recording studios, setting up equipment or "rigging" for small productions and Radio experience has been commonly effective in helping your applications.Large broadcast companies hire interns for select job roles, some include the BBC, Channel 4, Channel 5 and ITV.
Something to work on and develop as a possible entry point, would be a social network. Networking offers many opportunities to individuals in the industry, meeting peers or people at conferences can benefit your future if you make bonds with select individuals. An understanding of software can also be developed to help your resume. Being able to use Adobe Audition for and Adobe Premiere Pro will prove useful when working alongside sound designers in the post-production process. Conveying a sense of passion in your application can benefit you massively, some employers look for passion and character in an interview rather than experience, therefore it is best to prepare for both possibilities.