It's rather like the infamous "Vulcan B.Mk.2A" which pops-up in just about every Vulcan book and article, or the "SR2" etc.
Controversy time again Tim,
The Vulcan SR very nearly
did exist, and it is mentioned in official publications, notably as "Vul Mod 003" This was a mod to upgrade the Vulcan to an SR reconaissance variant. This mod was later cancelled however, and appears to only have been intended for the B1 and B1a.
As an aside, a little more trawling today, turned up the fact that Mod 707, was to "Modify the R.A.T.O. instrument panel and electrical system, in line with latest requirements" and having read the mod, it lists several switches and indicators which were to be replaced, along with a number of cables. So it would appear that it was retained for use on B2's although how often, I have no idea. It also makes reference to the "R.A.T.O. Panel", although again, I have no idea where this would have been located!
Flipflopman