One ampere hour is a current of 1 ampere flowing for 1 hour. When you get an electricity bill, the electricity is measured in kWh which are kilowatt hours (in other words one kWh is 1000 watts for a period of one hour).
Watts are ampere hours mulitiplied by volts so, given a standard voltage of 240 volts in the U. K., it takes a current of just over 4 ampere hours to cost one unit of electricity on your electricity bill.
I hope that makes it easier to pay!