Hi Rob,
I was in pretty much the same situation as you. Did a degree in Aero Eng. Got diagnosed with PCKD on my mother's side. I was lucky enough to get a class 1 medical 2 years ago whilst the CAA were issuing initials with the OML restriction. I'm not sure if they still do this. My best advice is to get the medical done and see if they will issue you one. Quite a few of my fellow trainee pilots have OMLs for a variety of reasons and so far the recruiters I've spoken to have not mentioned anything about it being an issue with getting a multicrew job. It does however restrict you to multicrew work which in the current climate might be an issue. My advice to you. Get the medical done, get a job and go modular whilst you train and then hunt for a multicrew job. Or try and get on an airline sponsored program if you can afford it / if they are still open.