CORRECTED - UPDATE 3-C&W guidance cut overshadows demerger plans

(Corrects headline to "guidance overshadows demerger" from "guidance overshadowed by demerger")

* H1 EBITDA 463 mln stg v RTRS poll of 454 mln stg

* H1 revenue 1.86 bln stg v RTRS poll of 1.92 bln stg

* Says plans to demerge Worldwide business

* Revises down EBITDA forecasts due to Caribbean weakness

* Shares down nearly 8 percent

(Adds details, reactions, quote)

By Kate Holton

LONDON, Nov 5 (Reuters) - Cable & Wireless (C&W) (CW.L) cut full-year earnings guidance on Thursday due to a poor performance in the Caribbean, overshadowing a fresh bid to demerge the British cable group and hammering its shares.