Alan Day did not introduce to me Selecta Disc, John Brattan did.
The history of Selecta dates back to a market stall in 1967 ran by Brian Selby and his colleague Roy. Brattan worked at Syd Booths and became friendly with Selby.
They decided to open the legendary store in Arkwright St, Nottingham(later known as The Meadows).
Upstairs was dedicated to the College crowd led by Kev Thomas who later owned Arcade Records. Downstairs was the Soul Cellar which featured Dave Williams(the D in the label BJD, the others being Brian and John and Alan Day(who was born Alan Parkin in Horsley Woodhouse). Later to be replaced by Geoff Wheeldon(Swifty) and John Heathcote(Hector). Steve Elliott followed by John Blach.
I first encountered them on Mansfield market around '68 before venturing to Nott'm and purchasing Everyday People-Sly and the Family Stone in 1970(I think!) from Selby.
The early days saw them buying from FL Moore before importing their own from Kape Records, New York and others.
As I mentioned to my colleague Richard Searling and to many other close friends, I believe without Selecta Disc and their mass distribution of Northern Soul, I doubt the scene would ever have evolved in popularity. When you think back to the real golden era of interest, Selecta Disc were the suppliers of the bulk of the scene's interest. And even though some of the major label's knew there were the typical moody releases' in the shop, they more than compensated themselves by tapping into Selecta's finger on the trigger awareness.
Epic in particular used the Nott'm outlet to gauge whether to release Billy Butler, Sandi Sheldon etc.
Kev