How to remove someone's things from my garage

Five years ago my mother allowed a family friend to store items in her garage, supposedly temporarily. When she died her property including the garage passed on to me. The items remained and since I did not need the space immediately I did not press for their removal, although I made it clear that I wanted them taken away at some point. At first the person refused and became belligerant, and then earlier this year said they were making arrangments to take the things elsewhere. I believed them and have been waiting patiently but nothing has happened. I now need the garage urgently for storing my own things. The person insists I have to liase with them and demands to know what I am bringing into the garage - clearly intending to only make limited space available even though I want everything of theirs removed. No payment has ever been made or contract signed for using the space although the garage has been filled from top to bottom and front to back and it is not possible to put anything else in there. I want to know if I have any legal right to have someone else's property taken away by a clearance company, even though I resent the financial outlay and am afraid of any comeback as they have forbidden me to touch anything of theirs. There may be some valuable items in there although to me it looks like a lot of old junk. Can anyone advise the best (and legal) way of going about this?