I ran a 2.5mm SWA cable down the side of my garden before a patio was built, it runs under gravel round the side so could be removed if necessary.
Initially I was just going to put a 16amp connector at either end and use a jumper and something like this at the other end to connect it to the current outdoor plug. The outdoor plug is on one of two 32amp RCDs that serve the kitchen. I will be plugging in a flymo and probably outdoor lighting in the future.
Alternatively was going to put a fused spur off the existing 13amp outlet and hard wire the cable in. Would this be notifiable because it is external, or is it fine because it is an existing circuit?