I have a range cooker with 1 oven that is electric and runs on a 13amp plug instead of the usual hard wired cooker connection. The original instructions (now mislaid) said that it should be plugged into a 13amp outlet, not an extension. I cannot move the cooker to see the plate to verify the power consumption.The lead is 12 inches short of the 13amp outlet so I want to extend the lead using an inline connector. I can only find 10amp 3 pin inline connectors. Is this the max that is made and would this be safe to use with an appliance with a 13 amp plug.