I was looking in the Argos catalogue - it gives stats on how much electricity each of their fridges use (they don't seem to post this info on the online catalogue). Some were more efficient than others, but none had an 'A' efficiency rating. Some of the A rated larder fridges actually used less electricity than the 50L beer chillers.
Example - p 638 of Argos catalogue:
Cheapest 117 litre larder fridge (no freezer section) - uses 146kWh per year. Costs 99 pounds.
p650 of Argos catalogue, 89.99 for a 40litre beer cooler (with water dispenser) uses 602kWh per year. On same page, a beer chller which looks similar to yours - 292kWh per year. The extra 10 quid would pay for itself in electricity in a year! The most efficient one on the page was 219kWh per year - costs 129.99, but all are less efficient than the larger 117 litre fridge above.
Basically - buyer beware. If you have the space, get something more efficient - even if it is larger.