If its over fuelling, you can tell by smelling the fumes or checking out the spark plugs.
Bear in mind that in winter, its a lot more likely to consume more fuel. And that £60 of fuel doesn't go that far ...
£60 V Power is 46 litres ~ 10 gallons, which in winter, I usually get (mpg) low 30s, high 20s. So if you've covered 200+ miles, then you're on the money.
... Jeez, I remember when I started driving that £25 would carry you 200 miles!