Always plant close to the path or lawn, with unruly, fragrant plants like lavender spilling over and softening the edges.
You can always try lawn alternatives such as chamomile or creeping thyme to enhance the cottage look and bring extra fragrance. To help fill your borders, try mixing fruit and vegetable plants such as redcurrants, rhubarb and gooseberries.
This is quite common in a cottage garden as they were originally designed to be mainly functional. Peas, beans and cabbages also work well inter-planted amongst your flowers.