I am making a hard cheese and have waxed the cheese by dipping, but if mould does form under the wax, how am I to know. Does it appear through the wax? 

If the cheese is completely dry when you waxed it, mould is unlikely to grow under the coat. If still damp, the wax cannot stick allowing air pockets to form where mould is likely to grow. Mould is more difficult to detect under coloured wax, but if the coat is loose, there is a high chance you will find mould on the cheese.