We have had a family member do it. It was with Nuffield Health as we have a local hospital to us, they list their MRI costs on the local hospital website which was around £600 for the actual MRI then I think £200 for the consultant appointments of which there were two. It wasn't me so I am going off my memory.
Just google private MRI near me and see what comes up. All the costs were readily published as a ball park figure. The one above was for one area of the body to be scanned.