Hi @ Grumpy_Mike,
Thank you for your reply. I shall attempt to elucidate further.
Due to the way the light is (currently) dissipated by a single 4 pin RGB LED regardless of a frosted or sandblasted finish to the exterior of the bottles, I think I might (not 100% sure yet) need to use two W2821b's back to back as Paul _B has correctly surmised.
The W2821b strip I have is cuttable and has a self adhesive backing which should allow two LED's/pixesl to be stuck back to back then connected together in series via the solder tabs if folding them causes contact failure/snappage.