Its up to individual companies, councils or whoever is the employer, to decide for themselves if they want to offer 'enhanced' redundancy packages.
The government merely sets a minimum amount based on length of service and age. Usual rules are;
16-18 no redundancy pay.
18-40 one weeks pay per year worked.
41-64 1-1/2 weeks pay for each year worked.
64-65 as 41-64 but minus 1/12th for each month worked past 64
However, if your wage is quite high the redundancy is based on a government maximum figure, which at the moment I think is about £487 gross per week. If you earn more then your redundancy will be based on the £487 figure. If you earn less it will be based on your actual gross wage each week.
But as stated at the start, if companies want to pay more there is nothing to stop them.
One final note. All redundancy pay up to £30,000 is tax free and does not exclude you from certain unemployment benefits. (I think you are still entitled to Job seekers allowance). Anything over £30,000 is taxable at standard rate. (20%)
Havea look on the government website for more information and advice.