Contact CIPA the charted institute of patent attorneys they run clinics where they give free advice around the country as they are currently not running clinics, they may have some online advice they can direct you to, or let you know when there will be clinics back up and running.
Google patent attorneys in your area and contact them enquiring if they provide an introductary session for free, most do. A lot will do this happily over the phone. Just explain that you need more information.
In meantime do not disclose your idea generally to the public, but its fine to discuss it with a patent atttorney.
You can get advice through the goverment website gov.uk how to do searches to find out if the idea isn't already covered. But just becauase you haven't seen something before doesn't mean its a patentable invention. Thats where talking to an expert will help.
Someone above has said it will cost a lot to get a full patent in lots of countries, this is true but you dont need a full patent you just need to get an application on file, and then you will have a certain time period to promote or sell the invention. You can have a clear idea of what you need to put in upfront to assist in approacing third parties who may be interested in buying the idea from you.
This time is good for you to open discussions as they cant see what you have covered by your patent and therefore dont know if they can invent around it , There will come a time when you then have to decide if its worth proceeding with further which would be where major outlay would be.