My existing Hob & oven are connected via 2 flying 4 mm cables to a cooker connection outlet. I wish to move the hob (both hob & ovens new positions are within 2 m of isolator switch). The question is - what a reasonable max length for the flying leads. I want to be able to fix one of them on to plaster underneath the kitchen units- an over all length of 4 mtrs. I dont want to add wire into the plaster a a new connection outlet unless there is reasonable need - any comments ? thanks