Ah, I didn't get a code, I just clicked through the gig listing on the Spotify app and as I've got a premium account and it loaded a countdown clock I thought that was enough. Seems not.
Looking on the spotify forum someone contacted support and got the reply, "Codes are sent to artists' top listeners. If you didn't receive a code, I'm afraid you’re not eligible on this occasion."
So if you buy the records rather than stream, you're not going to get anything extra through spotify.