My apologies - though I wonder if the whole lot were PP fitted, as an online search shows 84018 and 84025 both PP fitted, and only the latter was SR.Photos of the Southern batch clearly show them fitted with V.C.R. - this is the extra gear on the side of the smokebox, also angular steampipes from the vac. gear. Because they were outside cylinders they had the VCR kit on both sides. Photos even show them with the extra vac. pipe, you might have though that it would not be replaced when its date was up. When they came back to the LM (swapped for Ivatts for standardisation) one was allocated to Wellingborough and used on P&P to Northampton.
Whether the intention was to use them on p&p or whether they were just built with VCR because that's what then drawings said is, I accept, another matter. But the S.R. system was air operated, I think (extra ?air tank on the M7s), so not suitable.
I don't have any relevant reference books.