Ah, right, so a few months before deregulation. Yes, that makes sense. That was when my then local route, the 145 went to Ensignbus; IIRC it was the second major transfer of routes to private operators (the first one having been the previous year, with the 81 to London Buslines, the 193 and W9 or "W-Niner" to Eastern National, and so on). I think it was the same date that the 217B went to Sampsons (and what a terrible operator they were, and what an unfitting colour scheme their buses had, when you could see it beneath the dirt, although it could look quite smart on coaches), the 283 to Scancoaches, and possibly the 200 to Cityrama.
Strange to look back and see which of those early tendered operators are still engaged with providing bus services. It really does seem to be the case that it really was the better operators that have survived in one form or another; while many that really weren't up to the job have gone to the wall (or refocused their energies in other areas).
But I digress somewhat