Completed sale on my house. However squatters are in the garage

Competed on my house sale 2 days ago. I got a phonecall today from our solicitors to inform me that the new buyers went to see the garage (it’s down the street from the house in a block) and apparently someone looked like they were living in there. We have never used our garage and it has been boarded up since we bought it 6 years ago. I Ofcourse assumed it was still this was so never bothered to check it recently.

I’m worried of being sued for breach of contract since this has not been sold with vacant possession. How would I do this? Can I just get the locks changed and the contents removed?