There is a handy reckoner as to statutory entitlement on https://www.gov.uk/calculate-your-redundancy-pay
Some employees will have a contractual right to enhanced redundancy pay. Most will have to put up with the statutory scheme.
Where there is doubt as to whether an employee may have other employment claims, an employer will generally seek to get the protection of a Settlement Agreement, in which case they will have to offer more than the minimum payment.
In addition to redundancy money, the employee will be entitled to his/her full notice period.