The responsibility of Government in relation to prices of goods and services generally is, in the main, limited to ensuring that markets are working properly for the benefit of consumers and of the economy as a whole. I am not aware of any particular difficulties in the market referred to in the question and, accordingly, one would expect any lower costs for suppliers to impact favourably on prices for the final consumer.
To assist consumers to take advantage of competition and to shop around for the best price there is a legal requirement under the Retail Price (Diesel and Petrol) Display Order 1997 for retailers to display the selling price of petrol and diesel per litre to consumers. The Office of the Director of Consumer Affairs is charged with responsibility for monitoring compliance with this order.