If you use stone chippings or wood chippings I would still dig out 100 mm ,put a treated timber edge !00mm in (Cheaper & quicker than concrete) , lay the terram, 75mm of type 1 ,compact , this will give you a path that wont sink , fill with water etc .. 25mm of chippings on top to make it look smart.The timber edge that you put in holds every thing about were you want it to be . If you just lay the chippingson the mud in a few months it will be all over the garden , & your be back to square one . It sounds like a lot of f**king about but in reality you should sort it in a day &