Place the chicken breasts on a board and slice each one in half horizontally to give you 8 thin slices. In a medium sized dish mix together the oil, half the lemon zest and juice, garlic, thyme, mint and pepper. Add in the chicken and toss to coat. If you have time cover with clingfilm and place in the fridge to marinate for half an hour. Heat a griddle pan over a medium heat. Season the chicken with a little salt and place on the hot pan. Cook for 2-3 minutes on each side or until cooked through. Meanwhile grill the rashers until crispy. Brush the bun halves with a little oil and toast under the grill. Mix the remaining lemon zest and juice into the mayonnaise. Spread the bottom half of each bun with a little mayonnaise. Then add the bacon, leaves, slices of tomato and lastly the chicken. Serve the remaining mayonnaise on the side.