If you believe there is a cartel in operation, the Competition Authority would be the best people to talk to, though I reckon they would expect fairly hard evidence.
petrol actually fell in Dundalk in the past week to 99.9c. however with the cold spell in the usa it appears the price of crude oil increased to nearly 60 dollars a barrell again. with the speed on lightning one dundalk garage has increased the price to 102.9 again. not so fast taking it down. I would also think that with the dollar at 1.30 to a euro that the price should reflect that. I know the old chestnuts ' taxes, vat, overheads etc will be trotted out but you have to admire the speed the garages can change prices when the price of oil goes up. beep beep as that cartoon character says.
if you are a retailer then the more you sell the cheaper you buy the product. So if you stop buying from the small local stations then their volume will decrease, so their costs will go up, then they will close down. It has happened in England and France, it will happen here too.