If you are filing a patent in the UK, you have to use the Patent Office (now known as the UK Intellectual Property Office). Before you approach the Patent Office you will need a drafted patent and drawings of your invention. To complete this you may well need a product designer to design your idea and sort out how it will work. (Patents are for how a new concept works not just the overall idea.) If you use an attorney they will handle the filing for you but alternatively you can self-file and the Patent Office has a team to support individuals filing applications themselves.
Want to know more? Use this link… Filing a Patent at the UK Patent Office