"Each socket (presumably for flat pin plugs) is designed to deliver a maximum of 13 amps - hence the 13 amp fuse you find in new plugs. Thus a double socket can supply no more than 26 amps. The current is given by dividing the power rating of the appliance connected by the voltage thus for a 250 volt supply a three kilowatt appliance will draw 12 amps.
Now, electric sockets are connected to the fuse/circuit breaker board by a ring main and this is fused (or circuit breakered) to a maximum of 30 amps (32 for circuit breakers) Hence one double socket supplying two three kilowatt appliances does not leave very much spare for other appliances connected elsewhere in the ring main. Depending on how old your wiring is, you may have one ring main wiring all the sockets in the house, or all the sockets on a floor, and in my house I have put a separate ring in for my kitchen. You can tell how many ring mains you probably have by counting the fuses you have at 30 amps (circuit breakers at 32)."
Already did before posting.