Employees who are members of the Scheme, contribute a percentage of their pensionable salary. The specific amount is agreed upon with your employer and the Trustees of the Scheme as part of the Special Rules, once your employer sign as a participating Employer in the Scheme. Member's contributions are at a minimum of 5%  of a member’s pensionable salary.

Yes.

You can make Additional Voluntary Contributions (AVCs) in multiples of 0.5%.  AVCs accrue interest on the same basis  as the compulsory contributions. However, where you opt to make AVCs, your employer shall not be under any obligation to match them with extra contributions.