Sorry, Dot, that is not right.
Woozer has done the decent thing and given the company more notice than contractually he/she has to. The company can't now turn around and demand that he leaves on a different date. They are effectively dismissing him - his contractual offer was to leave in January - and take all the holiday leave and public holiday leave as well. He is perfectly entitled to do this (unless something specific in his contract says he can't).
For such a dismissal to be 'fair' in the eyes of the law it must satisfy one of the fair reasons for dismissal. It doesn't.
The minimum statutory notice to be given in this situation is the longer of either:
1) what is specifically written in the employement terms (often one month)
2) one week per complete week of employement up to a maximum of 12 - so 11 weeks in the case of Woozer.
Go back and tell them that you consider that you are being dismissed by them, that you require to be advised what the reason for the dismissal is. Should get them running to someone who really understands the situation.