Dear Stiff...
I can empathise with you as I am in exactly the same boat with only slightly more hours and grade 1.
I have been trying now for what seems like years to land a twin charter job and from my experience charter operators seem to have a negative attitude towards guys like me who have instructed for the majority of their careers even though just over half of my total experience is instructional.
If you are like me and confident in your abilities as a pilot but can't work out why you can't get that illusive twin job you're not alone.
I have found the best opportunities for obtaining a job come through someone you know not what you know or your qualifications.
Thats my two bobs worth!