Company picking and choosing who and when re Redundancy?

I am have been notified I will be made redundant in next 6 to 8 months.

I have been fortunate to find a full time permanent job elsewhere.

I would be due a lump sum redundancy.

Company are refusing to let me go prior to my end date.

Union advise they will not step in as company have a business to run.

No one has left from my own department yet.

However others from other departments(large amounts) have been allowed to pick and choose when they leave? and still get package?

Can anyone advise if I have any route I can take to try and get company to give me package and be allowed to leave to take up new position?

Thanks

You have no rights. You can leave and forego the redundancy package if you like.