Dave,all is not lost yet! When B&O could still supply a replacement mech for the '9000,it included a ring magnet "clamper"as a solution to the spring clip problem.You should be able to get a suitable ring magnet from a model shop(Bob's Models in Yardley,praps?)this simply clamps over the disc,and holds it in place perfectly well.You just lift it off when changing the disc.Heath Robinson,but effective.If you need help with B&O kit,I'm local(ish)to you.
Regards,
Nick