Why has NMS 'got' to buy back shares. They have had authority to buy up to lower of 5mil Pounds and 10% of the shares for up to the latest NAV for at least a year. They have bought 3% and paid an average discount of 24%. In the last 6-monthly trading period, the NAV was 12.8p and yet they didn't buy any higher than 10.5p (if I remember right). Did they exhaust their 10% or 5mil pot? Nowhere near. They spent 1.5mil Pounds buying 3%.
Since they didn't reach their limit previously, I don't see how increasing this makes the slightest difference.
Of course, you can take them at their word that they will pursue a more aggressive policy. But that they didn't buy back more shares last time was not a limit of authority issue.