My puppy is only 11 weeks old, house trainning is going verry well, but he's getting over excited when he's done a doddle's as he knows he's getting a treat when its on the mat but with him bouncing about he's standing in it

How is house training going well, if he is 'doing it on the mat'. He is supposed to be doing it outside.

Pick it up as soon as he does it. But why aren't you training him to go outside.