It's a shame HMRC haven't increased the mileage rate since 2011. During that time, the cost of motoring has increased significantly.
Not so much due to fuel prices (although they have gone up), but due to taxation, insurance prices, and the cost of tyres and servicing (according to Epyx, who manage fleets totalling 4 million vehicles, car parts prices have increased by 35% in the last 4 years alone).