Are free publishing services, such as Globe Edit, worthwhile?
These types of publishers are often called vanity presses and as discussed in this question they have limited value. The press you are referring to, and why I think your question is unique, is:


  They want me to transfer exclusive rights to publishing my thesis, as a book.


That is a terrifying thought. That likely means you would be unable to (re)publish any aspect of your thesis as an article and may not even be able to use images in presentations. Your university and/or funder may also impose restrictions on giving away exclusive rights.