IMHO you should use Optimax or Ultimate or similar. There are a couple reasons I can see:
1) These fancy fuels have cleaning agents. It is a fact that a clean engine runs better. Over time, if you do not use these fuels, the performance of your engine will drop as the buildup around the valves etc. increases. Plus it will extend the longevity of the car. As Loony says if you are buying these cars and are reluctant to buy the "correct" fuel, maybe you should have considered a DCi.
2) Your car was designed to use 98RON. Some engines (I am not sure that the 182 is one, but I do believe it is) will adjust timing etc when it senses that the fuel is not upto par. Therefore you will see decreased performance, and more importantly if you are watching the pennies, you may see a worse MPG. So in the long run, using 95RON fuel may cost you money. Also because of this effect, looking at it for the other side of the fence, there maybe a perceived improvement in performance when switching up to 98RON, when in actual fact its the car running as normal.
Now as a choice between higher grade fuels??? That would have to be driver preference. If I were you and was worried about getting the best fuel for the car I'd try a tank of each and see which one feels best. It will not wreck the car to try. Nor will the odd tank of 95RON here or there if you are desperate.
To me the true test of these fuels will be in older performance engines that don't declare 98RON recommended and where the engine management doesn't change the parameters. Then you will see the true worth of them bhp wise.
Well that is my view and I will stick to Optimax thank you very much