We have a headtilt bun Wilson who became very poorly April 2009 with headtilt - which we didn't find the exact cause of
Wilson's thread is below which may be of some help - warning though it is very long, as we had another 2 sick buns at the time
http://forums.rabbitrehome.org.uk/showthread.php?t=178735&highlight=head+tilt+wilson
However, very long story short - we had Wilson on all sorts of different meds.
To start off with he was just on baytril (antibiotics), panacur & metacam - this was when his head was only slightly tilted. He then got progressively worse & his tilt changed sides - it was so bad his down eye was almost horizontal to the floor. We then changed him to steroid injections, depocillin injections & panacur - again sadly these did nothing for him.
He was having severe rolling episodes & we had to confine him to a padded cage for around 6 weeks. Eventually after bunny mad lisa on RU suggested it - we talked to our vet about Zithromax - it's an antibiotic that is used for humans & not licensed for rabbits, but Lisa had, had great results with it her for her headtilt bunny - so we felt we had no options left but to try it.
We switched him onto Zithromax & also started him on stemetil (human anti sickness drug) - continued with his panacur & I *think* his steroid injections. After just over a week of this treatment he was well enough to come out of his cage & go back with his partner Alice. We'd kept them in the same room at all times, but had to confine Wilson to a cage so he didn't hurt himself or Alice.
I have been told & read that the best way to deal with headtilt is to treat with as much strength of medication as possible - I think basically to try to beat the infection before it gets worse.
Wilson's head is still very tilted to this day - in fact his down eye is still pointing to the ground. However, he lives a completely normal life with Alice & bombs round their bedroom like a good un!! Occasionally he will have rolling episodes, but can right himself. The only thing I have to do for him now is keep a check on his down eye, as from time to time it does flare up with infection.
We also foster Angel another headtilt bunny for BARC - she came to us in September after being treat at PAH & then being put up for adoption with her friend Misty - Angie rescued them & both of them came to us. As far as we know it Angel was only ever treated with panacur - again she lives a completely normal life, just with a wonky head. You'd never know she'd been ill bless her.
Just so you can see how they can live with headtilt - this is Wilson with his wifey Alice
And this is Angel our foster bun
I don't know if any of this will help, but it might be worth mentioning the drugs we used to your vet to ask their views. Olly may be left with a tilt but it doesn't mean he can't live a full & active life.
Feel free to pm me if I can help further.
Sending your little lad lots & lots of vibes & hoping she'll be better soon, take care, Denise x