Is the engine management light on when running, if not does the bulb work?
£10 at £1.32/L is about 7.5 Litres, which is about 1.65 Gallons.
53 miles for 1.65 gallons gives just over 32 mpg, which isn't great, but it depends on how the car is used.
If you are driving hard with the car loaded up, wrong tyre pressures, dragging brakes and a leaky fuel line it's pretty good mpg.
If you drive efficiently, and the car has been professionally serviced (ie not just oil-and-filters changed at Kerbside Motors) it's pretty poor mpg.
If it's the latter I'd start by checking the coolant temp sensor and MAP sensor, easiest way to check is get it on some decent diagnostics and read the LiveData. These are not normally checked during service, and can put out faulty signals without putting the EML on.
hth
December 2011