To spatchcock the chicken lay the bird breast side down with the legs coming towards you. Feel along the spine and then cut (use a strong pair of scissors) along both sides of the spine from the parson's nose, cutting through the ribs to the next end.
Turn the chicken over and gently press on the breastbone so that the bird splays out. To keep the bird flat whilst cooking, use 2 skewers going diagonally opposite each other through the bird.
Combine the mustard, honey garlic, lemon juice and zest to slather over the chicken. Set aside for 20 minutes at room temperature or cover and refrigerate for up to 24 hours.
Spark up the barbecue or preheat the oven to 200C/fan oven 160C/gas mark 6.
Cook the chicken for around 45 minutes turning once on the barbecue until the juices run clear. You may need to partially cover any skin areas that begin to catch too much.
Combine all the ingredients for the slaw and serve alongside the hot chicken and wedges.