redundancy and holiday pay

My other half is involved in a redundancy situation since last November....voluntary redundancy turned into compulsory so union got involved. the result was long negotiations which have just been completed. In order to get company to agree to negotiate terms, the union agreed that the last month (mid Dec to mid Jan)would be considered working out notice. Some staff believe they are entilted to their full holiday entitlement i.e. 3 weeks as they have now worked into a New Year. company doesn't agree.
Anyone know what the situation is in these circumstance.

Thanks for you help.

You are entitled to 20 days holidays per full year of full time work.For part time or pro rata it is 8% of the hours worked.
So if 12 days were worked in January,1 days holiday would accrue.

Thanks Vandriver. Others believed that once the year starts (as a full time employee) your new year holiday entitlements also kick in, particularly when you must take any left over leave from the previous year by 31 December.