To use that much power he must have about 10 hairdryers on 24/7.
£1000 a month on electricity is absolutely huge.
Electricity bill is ~£370 per month, which is ~£12.33 per day.
At 20p per KWh this is around 62 units per day.
Assuming the business is open seven days per week, for 10hrs per day, we come to an average electricity use of around
6.2KW.
This is entirely plausible for a fast food business, if all the appliances are electric. Ovens, friers, lighting, air conditioning (possibly) would all very realistically add up to this. If the ovens etc are gas-fired then it's a different story; obviously gas is a lot more efficient for any kind of heating purposes.
As a point of reference, if you look
here you can see that around 6KW is typical for a small catering oven, with the hobs potentially adding another 6KW. This is before we add lights, aircon, kettles, microwave, friers, hot water etc.