The K series doesn't have a knock sensor so the higher octance won't increase performance. It will probably run a little smoother, and the additives will help clean the engine internals. Same kind of additives are found in Redex too.
Pros - will help clean internals, and run a little smoother. You might get a little more MPG but it's unlikely to be much if any.
Cons - costs more, and doesn't increase performance.
Can we have a sticky mods about use of higher octane fuels in our motors, pros and cons explaining the difference. Lots of people ask
As an answer use it by all means - you'll maybe see an increase in mpg (my k liked total excellium 4mpg more my honda/rover doesnt give a t*ss though). It wont do any harm-most say avoid supermarket petrol especially after tesco fiasco