Put chicken breasts - one at a time - inside a plastic bag and secure the top. Release some pent-up tension by beating those defenseless breasts until they're a uniform thickness. Put chicken breasts into a flat-bottomed dish. Into a small bowl, combine the garlic, wine vinegar, thyme, mustard, honey, red pepper/chilli flakes, sea salt & pepper. Mix well.
A few drops at a time, add in the olive oil, stirring after each addition.Pour marinade over chicken breasts. Cover with plastic wrap and refrigerate for 3 or 4 hours. Turn the chicken breasts over once or twice during the marinating. Preheat barbecue/grill. Remove from marinating dish, saving marinade. Put the marinade into a small saucepan and bring to the boil, then reduce the heat and allow marinade to simmer gently for 2 minutes. Spray barbecue/grill with a little cooking spray. Put the chicken breasts on the barbecue/grill and cover. Chicken should cook for approx. 5 minutes per side. Baste the chicken breasts every couple of minutes during the cooking process with marinade. Serve while hot.