Wiki says:
In the United Kingdom and Denmark (where Super Unleaded must be a minimum of 97 RON), V-Power has a rating of 99 RON (whereas V-Powers' predecessor Shell Optimax was rated at 98 RON). There is one other 99 RON fuel available in the UK, namely Tesco MOMENTUM99.
Tesco says:
Can't find the V Power Nitro+ official octane rating...