guys, many thanks for your input! I think it's now safe to say the Romanceers were a studio outfit and they recorded specifically for Pickwick.
As said before their recordings are pretty sparse on the orchestration side so I first thought the songs might have been demos. Now I think Pickwick simply tried to save money and hired just a few musicians instead of proper studio bands.
They have three songs on the album, all were chart hits around that time, "walking in the rain with the one I love" (love unlimited), "You're the man" (M. Gaye) and "First time I ever saw your face" (R. Flack). I'm not really into the Gaye and Flack covers but the Love Unltd. one is great. I prefer it to the original version.
The Chi-lites tracks are just the a- and b-sides of their 3 Blue Rock 45s.