Ask in the respective forums. The catalogts as such are not compatible. You will have to export your data from PSE and then reimport it in LR.
Lightroom can import directly from your PSE Organizer catalogs: Lightroom Help | Import photos from other catalogs. See these video tutorials as well.
I believe that for LR to detect the presence of a PSE catalog, you need PSE installed on the computer. So you could install LR on your current Windows computer and convert the PSE catalog to a LR catalog. Then you could move the LR catalog to your Mac and open it in LR there. LR catalogs can be moved between Windows and Mac. Your CC license will let you run LR on two computers, one Windows and one Mac.
Thanks John and Mylenium - will try that solution
Forgive me for what is probably a dumb additional question.
I understand the catalog is essentially a file pointing to the photographs and does not contain the photos themselves.
So I can see that I can get the catalog itself transferred over using this method, but how should I get the photos that the catalog references transferred from PC to Mac?
Thanks for all and any help.
Once you've transferred your catalog and folder hierarchy of photos to the new computer, the first time you open the catalog LR will complain that all of the photos in the catalog are missing. But you can use LR's "locate folder" command to relink the catalog with the root of the hierarchy, and all should be fine. See this article for details on migrating.