As long as you don't have any modifications, then just put 95RON in. The car may lose a little top end power, but if you're using it to commute, you're barely going to notice.
I've see people on the Facebook group claiming that the car MUST have 98RON as a minimum because "it says so on the petrol cap". Which isn't true (at least for my model year) - it says "Use 98RON fuel", but that's because it's recommended - there's no suggestion that you must ONLY use 98RON, or that anything less will cause your engine to explode. If you refer to the handbook, it does state quite explicitly that 98RON fuel is recommended for the best performance, but that 95RON fuel can be used with no detrimental effect other than slightly reduced power - but obviously, the inside of a petrol cap is a bit small to relay all that information so they just put "Use 98RON" on it.
If you're looking to save some money, which is perfectly understandable especially when doing high miles, then I'd just switch to 95RON and not bother with additives personally. Obviously this may not apply to modified vehicles which have been mapped specifically for higher octanes.