Cut the courgettes lengthways into slices of 3 mm thick. Arrange them neatly on the preheated ridged grill pan. Grill until the top side starts sweating and burn marks show through. Because courgettes are all water, this takes longer than other vegetables, at least 5 minutes. Season and turn and grill the reverse side for 3–4 minutes. Transfer to a serving dish and lightly oil. Adjust the seasoning, and serve with lemon wedges.