Hi Ash - Welcome to Go Morocco.
You can find cheap Flights from Birmingham to Fez, if the plane is not suitable considering the train or buses is a good and safe alternative. ONCF stands for the Moroccan railways office. There's connection between England to Fez via France and Spain. Supratours is a division of ONCF that offers international and national bus services, it was mainly established to serve and establish connection to places where the train is not accessible but I guess now they offer a full international/national service.
travelling by train (ONCF) or by bus (Supratours) is usually more fun and allow you to experience more Morocco.
I hope this helps, let me know if you need additional assistance. enjoy your trip and have fun