LONDON, Dec 21 (Reuters) - **British labour union Unitesays gives official dispute note to employers of North Sea oiland gas contractors over pay and working conditions
**Employers' association OCA and labour unions now have sixweeks to find a resolution before Unite will launch a vote onstrike action
**Unite and GMB unions say they are seeking a wage increase,better sick pay and paid travel time
**Companies represented by employers' association OCAinclude Amec Foster Wheeler, Petrofac and WoodGroup