Sacking? Or making redundant? There's a difference
Actually there is not. In the eyes of UK employment law, both are considered as as "dismissal". Both are subject to the laws of wrongful and unfair dismissal. A "fair" redundancy can be considered as a "fair" form of dismissal. An "unfair" redundancy can be fought on the grounds of wrongful or unfair dismissal.
There are dozens of websites which will detail the grounds and procedures for redundancy. And also hundreds of solicitors who will take up your case if you consider you have been unfairly stitched up.
By definition, voluntary redundancy is going to be "fair". Compulsory redundancy on the other hand, is often challengable. You probably won't get your job back, but if spot a flaw in the way you were selected, or the way the process was conducted, you may be able to negotiate a better redundancy payment.