Lesley,
My experience has been (and this is only my own personal experience) that some ENTs are very casual about precancers and early cancer because compared to all of the late stage cases they see, this stuff is no big deal. One thing you may want to do is have an oral pathologist read your husband's slides. An oral pathologist is a pathologist that specializes in just oral pathology and they are the real experts at reading the slides of oral biopsies. Most dental schools, like the University of Maryland, have Departments of Oral Pathology.
By the way, my surgery was not done until seven weeks after my intial biopsy for several reasons, one of them because I saw four head and neck surgeons and had I a difficult time deciding where to have treatment. It did not make any difference in the outcome of my treatment.
I'm glad your dentist saw the leukoplakia and that your husband had it biopsied and that it was precancerous. It needs to work that way more often.
Barb