Since arriving back in the UK I've been looking into the different accreditations, which are quite different from Singapore and may be confusing for those new to Reiki. Hopefully this summary will help if you are as confused as I was!
Firstly, you do not need any special accreditation to practice Reiki as a therapist or Reiki teacher in the UK. Reiki is still an unregulated field with individual Reiki teachers creating and certifying their own courses. With any certificate (as long as your attunements are done face to face) you will be able to get insurance and register with a Reiki Association to practice Reiki as a therapy in private practice (ie as a sole proprietor).
If, however, you are looking to work in the NHS or in a hospice/care home charity and get paid a salary for providing Reiki, you would probably need to be registered with the CNHC (Complementary and Natural Healthcare Council). This is a voluntary register for therapists who have met certain practitioner standards. These standards are quite arduous including 9 months of training, 75 documented Reiki treatments, an exam and assessments via an external assessor. Do note that there are very few jobs that pay a salary for Reiki, so realistically the majority of practitioners offering Reiki do so in the private sector, and are not CNHC registered.
For a Reiki practitioner who is seeing clients from home or a clinic and even as a Reiki teacher whose focus is teaching Reiki for self-care and self-healing, CNHC accreditation is simply not necessary. However, if you are wanting to take your practitioner training to a more "official" level, then CNHC accreditation may be something to consider, especially as this will become more important in the future as complementary therapies become more mainstream.
In a nutshell, if you are new to Reiki and wondering which teacher to train with, firstly consider what you are going to be using Reiki for. If it is for self-empowerment