Hi there
Personally I would choose Tesco Momentum,its usually cheapest fuel and give you very similar results like V-power in therm of power and MPG,although our cars(Subaru or EP3) preferred Tesco and car on Momentum has have smoother power delivery,with V-Power power delivery has been bit different in good way,I've check'd both fuels via det cans or via logs(I've logged on Syvecs knock reading and AFR/Lambda etc) and both have very similar characteristic
Yes fuel prices varies and its down to supply and demand,in London in some areas you can buy very cheap fuel,but in some areas where is only one fuel pump,normal fuel(95RON) can cost same money as most expensive V-Power,it really depends,I still remember when we are drove from Scotland and we are started to look on fuel and at one town,not sure where this has been,but somewhere around Leeds we are found Esso where normal 95RON has been sold for 1.45,when usually you can buy for £1.20 T99
And about the fuel millage,depends,we are managed on turbo conversion on EP3 with Syvecs around 330miles per tank,with K-PRO we are managed around 250-300miles...
And yes as above has been said,knock/det on Type R can cause serious damage,Knock control on Honda ECU is pretty good and should correct this,but you simply can expect when you put 95RON and car has been mapped on T99/V-Power ECU will correct this,yes ECU will correct this,but on det cans you will hear first probably big ping and then ECU will start to correct,due this if its only 95RON available use Octane Booster,if yours car have turbo or supercharger then I would stay off the boost until you will refill with correct fuel
Hope this helps
Thanks,Jura