Hi Paul,
I've finally sorted out access to the forums
I've been doing a bit of experimenting the past few years with pre-made composts as I had a few issues with my own mix.
The one that most of the bulbs I've tried with it seem to like is a continental orchid seedling mix. Basically bark, perlite and sponge, I then add a bit of moss and mix it up. They seem to do OK in it and it's very free draining.
Thanks
Lucas