I agree with checking to make sure the UTI is gone for sure. I've heard that cocker spaniels are nervous piddlers- but at the same time, he is still pretty young and I wouldn't be concerned yet. There is this website that explains the behavior development of puppies-http://www.petcaretips.net/stages-puppy-development.html. Your puppy might be going through the phase where he tests boundaries and dominence in the household. So I'd say, be firm and consistent in your discipline. Other ideas:
Restrict where he is allowed in the house, for example, only to one room for a couple days. If he doesn't pee, allow him into 2 rooms for a couple days. If he doesn't pee, allow 3 rooms, etc. (or however it is easiest to block off sections of your house). If he does pee, go back a step and restrict the space he's allowed in, if he doesn't pee, give him more space.
Another training tool I've had great success with is a spray called "Bitter Apple"- you can buy it in the pet store and it's primary purpose is to get dogs not to chew on something- BUT- I've found it is a great tool for learning other things. So, for example, if he pees on the floor- spray a squirt of bitter apple directly into his mouth (my vet told me to do this) and then once you clean up the pee, spray the bitter apple where he peed (test it out somewhere inconspicuous first to make sure it doesn't hurt your carpet- it never hurt anything I put it on but you know, be on the safe side). I don't know what that bitter apple is made of but my dog got to the point where no matter what my dog did wrong, all I had to do was show him the bottle of bitter apple and he would run away or stop doing whatever it was he was doing wrong. So that was a nice added benefit. It was a nice way to train him around company too because once he got to the point he didn't even like to see the bottle; when company came over, all I had to do was keep that bottle handy and if he jumped up on the guests, I showed the bottle and he stopped. Likewise if he started begging at the dinner table, showed him the bottle- he stopped.
Good Luck!