Gatecrasher,
I'm in (or was in) exactly the same predicament as you. (I'm a friend of rooftopartist) I've got thinner than usual corneas although my eyesight is so far perfect, and I have also been bumped 2 IOT courses having been told that I must wait to have a specialist appointment which so far has taken 6 months to come through. Hang in there!
Although I cannot speak for you (as who knows what goes on behind closed doors), I received a letter last week that said I'd been cleared to enter IOT next month. This is great news albeit confusing as I had previously been written to saying that my consultant was arranging for me to have a specialist appointment so as to rule out a condition called keratoconus (thinning of the cornea to a point it cannot focus the light sufficiently and vision becomes blurred) Is this what you have been told by any chance?
This appointment never materialised although soon after my pre-IOT medical I had to go for an ultrasound on both eyes at an eye clinic in Birmingham. If you are yet to receive such treatment it is painless and nothing to worry about.
At least now you know that someone else out there has similar eyes to yourself and has been given the all clear. I hope you receive a similar letter to that of myself in the near future. It may be that many people have thin corneas but perfect eyesight, but this has only been detected with the advancement of technology and what was highlighted as an anomaly is in fact no problem at all.
Let me know how you get on and very best of luck,
DangerMouse